Add a menu/window module

[Jigoku]

Would allow an easily uniform look for all menus, reusing the same properties.
Would also make titlescreen easier to modify.

[Jigoku]

Should be incorporated into the editor aswell at some point. Instead of right-clicking to remove an entity, have a small drop down menu appear with options to configure the entity.

Allowing copy/paste/delete as the basic functions.
Other entities (where required) will include movespeed, texture, force, etc.

[Jigoku]

Removing from 0.2 for now.

[Jigoku]

This will need to be done soon, as the entity menu in the editor is getting cramped up / hard to navigate. Editor needs an overlay menu that can collide with the mouse to select the active entity type for placement.