tools: add README

tools/README.md

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+# Tools directory
+
+### `coin_info.py`
+
+Central module that extracts information from jsons in `defs/` directory.
+Its most important function is `get_all()`.
+
+### `coin_gen.py`
+
+Code and data generator. Has the following functions:
+
+* __`check`__: runs validations. Currently, that is:
+  * schema validity in `defs/coins/*.json`
+  * availability of bitcore/blockbook backends
+  * icon format
+  * support data, i.e., that `support.json` matches the rest of data
+
+* __`coins_json`__: generates `coins.json` for use in python-trezor, connect
+  and wallet. By default outputs to current directory.
+
+* __`coindefs`__: generates `coindefs.json`, intended future format for sending
+  coin definitions to Trezor.
+
+* __`render`__: for every `filename.ext.mako` passed (or for all found in directory),
+  renders the Mako template with coin definitions and stores as corresponding
+  `filename.ext`. This is used to generate code in trezor-mcu and trezor-core.
+
+### `coins_details.py`
+
+Regenerates `defs/coins_details.json`, which is a catalog of coins for https://trezor.io/coins.
+
+All information is generated from coin definitions in `defs/`, support info is
+taken either from `support.json`, or assumed (see `coin_info.support_info()`).
+
+If needed, any value can be overriden in `coins_details.override.json`.
+
+### `support.py`
+
+Support info management. Ensures `support.json` is in the proper format. Has the
+following subcommands:
+
+* __`rewrite`__: regenerates `support.json` in a canonical format, i.e., only
+  mandatory fields in fixed order.
+
+* __`check`__: checks validity of support data. This is the same check
+  that runs as part of `coin_gen.py check`, except missing support data is always
+  an error.
+
+* __`show <keyword>`__: searches coin database, matching key (`coin:BTC`),
+  name ("Bitcoin") or shortcut / ticker symbol ("BTC"). Displays all coins that match
+  and their support info, if found.
+
+* __`set <key> [symbol=value]...`__: updates support info for coin key (`coin:BTC`,
+  can be found with `support.py show`). Basic `symbol`s are: `trezor1 trezor2
+  connect webwallet`. Anything else is considered a link name:
+  `"Electrum=https://electrum.org"`  
+  Allowed `value`s are `yes`, `no`, `soon`, `planned`, URLs and firmware version
+  numbers. Empty value (`trezor1=`) clears the respective symbol.
+
+### `requirements.txt`
+
+List of Python requiremens for all tools in `pip` format. Set up your environment with
+`pip3 install -r requirements.txt`, or `pipenv install -r requirements.txt`.
+
+Python 3 is required, recommended is 3.6 or higher.