CheckJira: Re-order some checks

The order of checks is changed from (unresolved > status > issuetype)
to (issuetype > status > unresolved) so that it goes from the more
general to the more specific.

This also changes some of the error messages.
Add global $Git::More::CONFIG_ENCODING

This global variable tells get_config which encoding is used in Git's
configuration files so that it can decode them appropriately.
Normalize branch names gotten from Gerrit

When Gerrit mentions a branch name via the hooks arguments it uses the
branch short-name if it is in the refs/heads/ namespace. But we need to
normalize on the long-name, so we detect short-names and convert them
into long-names here.
CheckJira: tell the user which issuetypes and statuses are approved