now using a minimum texture size for filters (closes #312)

to avoid constant texture recreation when filter region gets small.
auto-trimming number of used quad batches (closes #329)
now using a stable sort algorithm for 'sortChildren' (closes #304)

It's a merge sort algorithm that doesn't do any allocations while it runs.
fixed mergeSort result order
fixed draw count display

It was wrong when there were only quads on the stage (no images).
added 'alignPivot' method to DisplayObject class (closes #293)
added optional 'id' paramter to 'TouchEvent.getTouch' method (closes #198)
now removing text field from Button if text is empty
now logging warning when adding the same asset name twice (closes #339)

Previously, an exception was thrown.
Merge remote-tracking branch 'PrimaryFeather/master'