* Support passing CKeyID to CMessageSigner/CHashSigner
* Use Dash addresses instead of raw public keys for sporks
The spork addresses are identical to the previously used public keys.
Also use CKeyID/CKey directly inside CSporkManager instead of parsing the
addresses/keys over and over. The default spork key (from chainparams) is
initialized with InitDefaultSporkAddress(). SetPrivKey parses the private
key now and stores it in sporkPrivKey instead of parsing it in
CSporkMessage::Sign().
* Allow setting of spork address via command line
* Remove unused strMasternodePaymentsPubKey chainparam
Traces from the past...
* Review fixes
1. Remove the need for InitDefaultSporkAddress
2. Remove bogus checks for hex private keys
3. Alphabetical order for new include
4. Add . to help string
* Add regtest spork key
As this key is not meant to be private, the private key is also added in
the form of a comment (for later use in regtests)
* Review fixes
