Added StretchableButton, you can change it size by dragging.
Comments addressed.
Adjusted EditorGameAssets#resolve and test fix.
Merge pull request #667 from gorco/StrButton

Added StretchableButton.
Merge pull request #663 from RotaruDan/FramesTimeline

Frames timeline
Small default FocusItemStyle improvements.
Adds necessary actions and tests.
FocusItemList and LinearLayout improvements.
Renamed FramesTimelineTest to AnimationEditorTest.
Adds AnimationEditor.
Still needs some functionality, waiting for #668 to get merged.
FramesTimeline and FrameWidget refactoring. Adds duplicate and delete functionality.
Adds PreviewView.
Convencience methods and attributes.
Moved external resources to images folder while testing.