Core user data and leaderboard commands.

Added flexibility to data `update_where`.
Added interactive utils, with improved pager.
Added user data table, with caching and transactional interface.
Added `topcoins` command to `Economy`
Added `top` command to `Study`

bot/core/__init__.py

@@ -0,0 +1,2 @@
+from . import tables
+from .user import User