gitk feature request: checkout any commit

Hello,

it would be helpful, if gitk would allow checkouts not only for local branches but also for remote branches and any other commit.

For remote branches, it is sufficient to remove the code that greys out the context menu. The context menu for regular commits would need a new entry.

Of course, this can easily be done via command line - but that's true for every gitk feature :)

Another feature that would really suit gitk is the "Tools" menu from git-gui. A simple 1:1 copy would be fine ;)