s/bitcoin/Bitcoin/
Change license to LGPL v3 or later

LGPL is compatible with any reasonable usage of the software. In
particular with security-related software users should demand access to
sourcecode for auditing.

Prior license for most code was MIT, which is compatible with LGPL. One
exception was bitcoin.rpc, which was LGPL v2 or later, so this relicense
brings us into 100% compliance with that code's license.