Add a reset command to be able to reset a remote to a previous commit

to fetch changeset again.

Could be useful when you mess something, change a changeset message, want to better handle a merge commit...
Ex: 
http://stackoverflow.com/questions/17279814/how-can-i-clean-up-a-broken-history-with-git-tfs
http://stackoverflow.com/questions/11393180/git-tfs-reset-to-remote/11393702#11393702