Adds Mod Options

Used by mods for client side configs (though it doesn't prevent common). To add a new GuiModOption follow the steps below :)

1 ) Create a GuiModOption subclass.
2 ) ClientRegistry.registerModOptions(modName, GuiModOptionSubclass)
3 ) Done!

From what I've read up, there is an intention to add a gui library if I grasped it correctly. My response to that ahead of time is that I believe that is a great idea, but shouldn't prevent this to be pushed since the planned release of this library is (in my mind) currently unknown.

If you need me to improve the code, I will gladly do so. This is my first pr to FML so I understand that it may be in bad form.