Msysgit remote hg rebased

Hi there,

so I took the remote-hg changes from the msysgit repo, and rebased them on the current git.git master -- mainly so I could test it with the latest git, and compare it against https://github.com/buchuki/gitifyhg. Also, git.git master contains some changes that make some of the in the msysgit remote-hg obsolete -- I dropped three patches. And of course there were lots of conflicts, e.g. due to git-remote-testgit having been renamed to git-remote-testpy.

Since I thought you might perhaps interested in this, I am filing this pull request. It also contains a commit which fixes cloning SSH repositories, which you could cherry-pick if you like...

Sorry for the gigantic diff, but most of the commits in this PR are only there because msysgut/master is a lot behind git.git master, and I wasn't sure what other branch, if any, to base this upon.