C: ModuleManager, SpellFrame, Module Load

Misc optimization.

Renamed SpellFrame.backdrop to SpellFrame.frame for consistency with
SpellBar implementation.

Added SpellFrame:hide() and :show()

Fixed bug when activating/deactivating spellbars which were inactive.

Added module saved var API.

Added module function hooking for various events such as
SpellBar:Hide(), SpellFrame:refresh_settings() and the like.

Moved/added spell_bar_sort utility sort function to use as sort method
w/ spairs to iterate in-order over a table of spell bars.