magit-delete-branch: fix bug missing ':' before branch name when branch
is remote.
Merge pull request #1026 from shigi/fix-delete-remote-branch

magit-delete-branch: fix bug missing ':'
rename magit-{cherry,status,wazzup}-{insert- => }-sections-hook

I intended to do this earlier but forgot to do it.  Because users might
already have customized these hooks using the old names, add aliases for
the old names, but define them as obsolete.
magit-wash-log-line: don't show "tag: " prefix as a ref

`git log --decorate' prefixes tags with "tag: ".  For a short time
we treated this prefix as a separate ref, and stop doing so now.