Fixes issue #232.
It assumes largest possible signature size for all inputs. For segwit
multisig it can be .25 bytes off due to difference between segwit
encoding (varint) vs. non-segwit encoding (op_push) of the multisig script.
The 4 byte hash_type/forkid is part of the signed message, but not
part of the transaction. Instead of hacking it into the transaction,
add it after the transaction when computing the signature.
Having CoinType using the protobuf structures has several disadvantages.
- We always need to change trezor-common if we need a new field (like
bech32 prefix)
- Every time Trezor initializes it sends all this information out and
nobody cares.
- The protobuf structures add storage overhead due to their fixed size.
I also removed most of the `has_` fields except for forkid:
- `has_segwit` was merged with segwit
- `has_coin_shortcut` can be replaced by test for NULL if necessary.
The fields were reordered for better padding.
