CH05::best practices/using wallet: remove these sections

The previous version of this chapter focused on a single set of
technologies: BIP32 HD wallets, BIP39 seeds, and BIP43/44 paths.  The
previous Best Practices section described these as a de facto standard.

In the rewrite of this chapter, we've introduced several alternatives
for BIP39 seeds and BIP43/44 paths, all of which are good practices.  I
have my opinions about what might best, but I think it's entirely
possible for a reasonable person to conclude one of the other choices is
best, so we remove that section.

The Using A Wallet section was redundant; we've already introduce all of
those concepts.

ch05.asciidoc

@@ -581,109 +581,6 @@ increasingly adopting support for explicit paths using descriptors.
 Applications which do both will usually conform to the standards for
 implicit paths and also provide descriptors.
 
-==== Wallet Best Practices
-
-((("wallets", "best practices for")))((("bitcoin improvement proposals",
-"Multipurpose HD Wallet Structure (BIP43)")))As bitcoin wallet
-technology has matured, certain common industry standards have emerged
-that make bitcoin wallets broadly interoperable, easy to use, secure,
-and flexible. These common standards are:
-
-* Mnemonic code words, based on BIP39
-* HD wallets, based on BIP32
-* Multipurpose HD wallet structure, based on BIP43
-* Multicurrency and multiaccount wallets, based on BIP44
-
-These standards may change or may become obsolete by future
-developments, but for now they form a set of interlocking technologies
-that have become the de facto wallet standard for bitcoin.
-
-The standards have been adopted by a broad range of software and
-hardware bitcoin wallets, making all these wallets interoperable. A user
-can export a mnemonic generated on one of these wallets and import it in
-another wallet, recovering all transactions, keys, and addresses.
-
-((("hardware wallets")))((("hardware wallets", see="also wallets")))Some
-example of software wallets supporting these standards include (listed
-alphabetically) Breadwallet, Copay, Multibit HD, and Mycelium. Examples
-of hardware wallets supporting these standards include (listed
-alphabetically) Keepkey, Ledger, and Trezor.
-
-The following sections examine each of these technologies in detail.
-
-[TIP]
-====
-If you are implementing a bitcoin wallet, it should be built as a HD
-wallet, with a seed encoded as mnemonic code for backup, following the
-BIP32, BIP39, BIP43, and BIP44 standards, as described in the
-following sections.
-====
-
-==== Using a Bitcoin Wallet
-
-((("wallets", "using bitcoin wallets")))In <<user-stories>> we
-introduced Gabriel, ((("use cases", "web store", id="gabrielfive")))an
-enterprising young teenager in Rio de Janeiro, who is running a simple
-web store that sells bitcoin-branded t-shirts, coffee mugs, and
-stickers.
-
-((("wallets", "types of", "hardware wallets")))Gabriel uses a Trezor
-bitcoin hardware wallet (<<a_trezor_device>>) to securely manage his
-bitcoin. The Trezor is a simple USB device with two buttons that stores
-keys (in the form of an HD wallet) and signs transactions. Trezor
-wallets implement all the industry standards discussed in this chapter,
-so Gabriel is not reliant on any proprietary technology or single vendor
-solution.
-
-[[a_trezor_device]]
-.A Trezor device: a bitcoin HD wallet in hardware
-image::images/mbc2_0504.png[alt]
-
-When Gabriel used the Trezor for the first time, the device generated a
-mnemonic and seed from a built-in hardware random number generator.
-During this initialization phase, the wallet displayed a numbered
-sequence of words, one by one, on the screen (see
-<<trezor_mnemonic_display>>).
-
-[[trezor_mnemonic_display]]
-.Trezor displaying one of the mnemonic words
-image::images/mbc2_0505.png["Trezor wallet display of mnemonic word"]
-
-By writing down this mnemonic, Gabriel created a backup (see
-<<mnemonic_paper_backup>>) that can be used for recovery in the case of
-loss or damage to the Trezor device. This mnemonic can be used for
-recovery in a new Trezor or in any one of the many compatible software
-or hardware wallets. Note that the sequence of words is important, so
-mnemonic paper backups have numbered spaces for each word. Gabriel had
-to carefully record each word in the numbered space to preserve the
-correct sequence.
-
-[[mnemonic_paper_backup]]
-.Gabriel's paper backup of the mnemonic
-[cols="<1,^50,<1,^50", width="80%"]
-|===
-|*1.*| _army_ |*7.*| _garbage_
-|*2.*| _van_ |*8.*| _claim_
-|*3.*| _defense_ |*9.*| _echo_
-|*4.*| _carry_ |*10.*| _media_
-|*5.*| _jealous_ |*11.*| _make_
-|*6.*| _true_ |*12.*| _crunch_
-|===
-
-[NOTE]
-====
-A 12-word mnemonic is shown in <<mnemonic_paper_backup>>, for
-simplicity. In fact, most hardware wallets generate a more secure
-24-word mnemonic. The mnemonic is used in exactly the same way,
-regardless of length.
-====
-
-For the first implementation of his web store, Gabriel uses a single
-Bitcoin address, generated on his Trezor device. This single address is
-used by all customers for all orders. As we will see, this approach has
-some drawbacks and can be improved upon with an HD wallet.((("",
-startref="gabrielfive")))
-
 === Wallet Technology Details
 
 Let's now examine each of the important industry standards that are used