This commit explicitly ignores errors that were already intentionally
ignored in btcctl by using an _ to make the errcheck utility happy. It is
also nice to make it explicit that the error is being ignored
intentionally rather than leave questions of whether it was accidentally
forgotten.
This commit adds version information to btcctl. The plan is to keep
it in lock step with the btcd version. It also updates the release script
so the version file is updated automatically with the btcd one.
