source distribution for charmstore deployment.

Adapted some scripts I've used to freeze a source distribution of the charmstore, for past deployments into a restricted build env.

Since the source build manipulates its own GOPATH, and does some rather drastic things (like git reset --hard), I think its probably safer to keep this stuff in a separate makefile that probably won't be used during normal development.
Since we've moved juju/charmstore to github do we want to keep this branch on Launchpad still?