peer: introduce peer methods to prepare for peer classes This introduces a peer method into all repository classes, which currently simply returns self. It also changes hg.repository so it now raises an exception if the supplied paths does not resolve to a localrepo or descendant. Finally, all call sites are changed to use the peer and local methods as appropriate, where peer is used whenever the code is dealing with a remote repository (even if it's on local disk).

bookmarks: document behavior of -B/--bookmark in help

test-bookmarks-pushpull.t: verify correct push -B behavior I wasn't able to find a test that proved this behavior worked, so I felt obligated to write a quick test so it won't regress in the future.