Removes the leading 0 from the version number. The minor version, which
we had been using as the major version, is now the major version. The
revision, which we had been using as the minor version, is now the minor
version. The revision number is dropped. The build number is promoted to
being part of the version number. This also avoids issues where it was
accidentally not included in the version number.
The CLIENT_VERSION remains the same format as previous as previously,
the Major version was 0 so that was never a factor in CLIENT_VERSION.
This adds an executable `bitcoin-rpc` that only serves as a Bitcoin RPC
client.
The commit does not remove RPC functionality from the `bitcoind` yet,
this functionality should be deprecated but is left for a later version
to give users some time to switch.
