Found a bug in FramesComponent while making repo entities that made nested frames not work properly
Merge pull request #939 from jtorrente/nestedframesbug

Found a bug in FramesComponent while making repo entities that made nest...
Using gameAssets to resolve dependencies in ScaledTextureLoader instead of the file.sibling() method, which causes null pointer exceptions in engine
resolve() method unified in EditorGameAssets and GameAssets
Bug fix in DesktopPlatform - null ImageUtils returned caused NullPointer in repo builder
Bug fix in EditorDemoBuilder - recent changes in api caused games saved by Json in EditorDemoBuilder be not readable
Moving method getRendererDimension from RepoLibraryBuilder to parent class EditorDemoBuilder - needed for next commit
Methods added to automatically center origin in elements created with EditorDemoBuilder. Applied to PlanesDemo, to see if bug gets fixed https://github.com/e-ucm/ead/issues/937. Not lucky :(