added internal info methods: %branches and %remote_branches

%branches means "local branches"
added Git implementations for both
this exposed a bug in `vc info`, which was trying to do a double `deref` on info methods (now fixed)
made info expansion of ArrayRef methods in code work

also tweaked some erorr messages which made my life a bit easier while debugging
lots of new info method tests
very simple docs for action directives

hopefully this is just a placeholder for better, more complete docs to come
new info method: %tags
bugfix for %cur_branch

it _is_ possible for `git branch --contains HEAD` to return multiple branch names (who knew?)