Module unloading and reloading

[phst]

Continuing from #28 so that we have one issue per problem.

Currently both unloading and reloading a module are impossible. I think these operations should be defined to bring modules on par with Emacs Lisp libraries, if feasible, but we need to be careful to correctly define them and not put a large burden on module authors.

[PhilllyJoy]

#28 requests only module reloading, and only for use during module development - because faster dev cycles are a big win. What you're suggesting on the (IIUC) is having both unload and reload for users which is tougher technically and therefore a debating hazard on emacs-devel.

I doubt it the latter will get anywhere without months of bikeshedding and chest-pounding on the ml, and It would be a shame to delay/lose the former because the latter gets resistance. It's perhaps a good idea to consider the two to be seperate features and start with the one that doesn't impact users.