* Added camera buttons.
* Added poll to check on active object type.
ToDo:
* Lens Unit "lens" and "angle" don't update each other. Needs RNA fix.
* Buttons only work for default camera now, needs better context.
* Made separator item work horizontal & vertical.
* Add colon (:) automatic for int/float/enum/string.
* Added space variables to uiStyle and use them in the
layout engine.
* Added initial World buttons by Thomas Dinges, thanks!
* Added some code for modifiers in the Object Data context.
This will become a template though.
* Use a common poll() callback in the scripts to reduce code.