Selection in context is inmuttable, so java arrays instead of lists
New scene elements are added to the center of the scene
according to the viewport
Fix in filechooser
Adde close action
Widgets are not updated until an object is read
EditorDesktop refactored, title now shows path too
View events
Some renames
GUI test for back next buttons
Better events in Spinners
Moved some widgets to dragndrop package.
Removes Cell#ignore(), libGDX removed that method when forked TableLayout.
Adds DraggableLinearLayout, supports dragg'n drop via events.
FocusItemList supports selection via events.
Changes FramesTimeline to use the new FocusItemLIst features.
Changes AnimationEditor to use the new FocusItemList featues.
Small changes to AnimationEditorTest.