Added btcreset tool

This should make the process of updating all your monetas repositories a little easier.

Problem: "go get -u" only does fast-forwards

If the repository is rebased from conformal, for example, go get won't update that repository, leading to problems.

Solution: btcreset

Will go into each monetas repository, checkout the master branch and do a "git reset --hard origin/master". Note all such repos will have their changes "git stash"ed. If there was a recent autorebase, this tool should set everything right again.