Added Render Element Manager.
TODO: Support for adding elements, and missing methods.

Signed-off-by: Daniel Santana <danielgsantana@gmail.com>
Added new methods.
TODO: Maybe we could use the Animatable returned by the FPValue for the
render element, using the PB2 for getting the properties.
Add new ignored files.
Merge pull request #1 from dgsantana/master

RenderElementManager