Fixes TiledMap layer ordering in Objectmakers (2D & starling)

Problem before:
The order of tile layers and object layers (internally called objectgroups) are only considered separately. Object layers will always be in the foreground. This causes problems if objects in an object layer have the view parameter set.
Example: A background object with an image as view will always cover all tiles.

This fix resolves this issue by taking the total order of tile and object layers into account. 

As small bonus I also fixed the FIXME in Objectmaker2D (semantics issue).

Tests:
I tested the Objectmaker2D case in my own project and the starling case with the given example from the Citrus-Engine-Examples repository. The ordering of tiles and objects were as defined in the TiledMap editor. This resolved my object view problem.