timob-12816: clean up and improve image view.
1. Use both memory cache and disk cache.
2. Don't pre-scale the images in our code. Let native Android take care of scaling.
3. Download and decode bitmaps in the background thread so it won't block the UI.
Merge branch 'master' of git://github.com/appcelerator/titanium_mobile into timob-12816
timob-12816: add support for auto rotate in TiImageView. resolve merge conflicts.
timob-12816: 1. Move retry decode to getBitmap().
2. Remove TiBackgroundImageLoadTask.
3. Add TiLoadImageManager which uses unbounded pool.
timob-12816: set default image in UI thread
timob-12816: small fix
timob-12816: address comments
timob-12816: small fix
timob-12816: modify the function name
timob-12816: need to call super if width or height changes
timob-12816: In TiLoadImageManager, each image needs an arraylist to hold all the listeners.
timob-12816: cannot set AdjustViewBounds to true when using ScaleType.MATRIX, because setAdjustViewBounds(true) is equivalent to setScaleType(ScaleType.FIT_CENTER).
Merge pull request #3936 from pingwang2011/timob-12816

timob-12816: clean up and improve image view