Bip-utils

- Fix `BipCoinBase.ComputeAddress` method, raising exception in case of invalid address class

- Improve and simplify coin configuration so that it's easier to read, modify and maintain
- Add classes for private and public keys that are in charge of getting keys with different format
- Refactor `Bip32` class
- Move exceptions to separated files
- General code re-factor and improvement

- Fix minimum depth for public derivation (set to account level)

- Fix bug in `PathParser` class
- Refactor `PathParser` class
- Add possibility to use `p` for hardened indexes, e.g. `m/0'/1'` is the same of `m/0p/1p`

- Add some simple methods to Bip classes: `Bip44Base.SpecName`, `Bip44Base.CoinNames`, `Bip44Base.IsCoinAllowed`, `Bip44Base.IsPublicOnly`, `Bip44Base.IsTestNet`
- Add `GetConfig` method to coin helper classes, remove `GetWifNetVersion` method
- Export `EntropyGenerator`
- Rename `Bip32.IsIndexHardened` to `Bip32.IsHardenedIndex`
- Remove `Bip32.SetTestNet` method
- Remove useless exceptions
- Add support for Dogecoin BIP-0049
- Fix DASH WIF main net version and Dogecoin test net versions

- Add support for DASH coin (both Bip44 and Bip49 are supported).
- Add *key_helper* module for checking if a key is private or public compressed/uncompressed.
- Add error checking to classes that generate addresses (`P2PKH`, `P2SH`, `P2WPKH`, `EthAddr`, `XrpAddr`). They now raise a `ValueError` exception if the provided key is not valid
- *WIF* module checks for key validity when encoding; when decoding, it checks if the resulting key is valid