Add purpose codes

Given a complete lack of response on the bitcoin-development
mailing list we have no assurance that these proposals will ever
be assigned a BIP number, therefore we can not rely on having one
in order to derive a purpose code.

The purpose code is drived by from a string:

"V" signifies voting pools
"B" or "C" for bulk or colored coin wallets, respectively
a version number between 00 and 99
clarify public deriviation for colored coin levels