Common Scripts for user-created levels should be removed

When a level is put together, the ScriptManager appends the user's scripts with common scripts. Currently, it looks like these common scripts support a help-like system involving Captain Anya.

We should get rid of commonScripts for two reasons:

1. Greater flexibility in level creation (i.e. if somebody wants to create a level where Anya is not present).
2. More transparency to the end-user, nothing being added to their level without them knowing.

The commonScripts are loaded in lines 16 and 69 in ScriptManager:
https://github.com/codecombat/codecombat/blob/master/app/lib/scripts/ScriptManager.coffee

And exist here:
https://github.com/codecombat/codecombat/blob/master/app/lib/scripts/commonScripts.coffee