ThreeThree

Requesting merge for:
- MOSYNC-2792 "Add path support for image widget."
- MOSYNC-2818 WP7 Back button: implement the event propagation inside the runtime and send an event to mosync when the back button is pressed.
- MOSYNC-2856 StackScreenTest: application exits on back button.
- MOSYNC-2828 On wp7 platform 'maGetScrSize()' returns the same values disregarding the screen orientation
- MOSYNC-2829 WP7: undesired behavior of the back button inside a webview
- MOSYNC-2832 Add path support for image button widget.
- MOSYNC-2790 Add pressed image to image button on NativeUI.
- MOSYNC-2817 As a developer I want to get an event when the back button is pressed on windows phone 7.
- MOSYNC-2881 As a developer I would like to be able to get a Screen from a StackScreen by index
- MOSYNC-2795 Screen Transitions on Stack Screens
- MOSYNC-2787 Upgrade IAP to In-app Billing Version 3 API on Android.
- MOSYNC-2923 WP7: calling the ''maExit" syscall on wp7 closes the app with an unhandled exception