- move bitcoin wallet links from coins_details.override.json to a separate
wallets.json file
- drop NanoWallet links from nem nem_mosaics.json, auto-add them in
coins_details.py instead
- move misc wallet links to misc.json
- clean out override file
- change wallet format in coins_details.json:
- they're now list instead of dict, so that we can specify ordering
- add Trezor Beta wallet link to ETH/ETC and their tokens
- somewhat stricter checking of trezor.io wallet data
* btc-like coins are now called `coins`, with key type `coin`,
for consistency with names in other tools
* `others` are renamed to `misc` and placed in a separate subdir
* added many docstrings that explain the behavior
* renamed and privatized many functions
