[Android] Launch Screen 2nd-step implementation

This is the second step implementation of Launch Screen feature.
As the spec defined, the launch screen contains 3 layers:
1. background color
2. background image
3. foreground image
It's impossible to show all these layers together when user tap on the icon,
because of the limition of Android drawable system.
And the actual flow will be as below:
Display the first 2 background layers, and then display the 3rd layer foreground image.

Below is the description for the implementation in general:
Build scrip:
1. Parse manifest.json and customize launch screen
   1) Generate drawable: launchscreen_bg.xml
   2) Parse backgroud and foreground image.
2. Copy background image and foreground to res folder.
Runtime:
1. Create a new layout to display 9-piece format foreground image.
2. Parse image-border from manifest.json, and customize the layout.

TODO:
On feature missed in this patch:
'ready_when' = 'user-interactive', This feature is currently under investigation,
and need to hook from content side, will support it in another patch.

Spec: https://docs.google.com/a/intel.com/document/d/17PuNuHRTQuREUpaCvj-eEx7uYi2avd-VW-oaMXMpvwo/edit?pli=1#
Design Doc: https://docs.google.com/a/intel.com/document/d/1YLajlZC7CkBOtEvzD6p6yeBr0HrPsaIGX8Eqhr3oTF4/edit#heading=h.mfsu3bk9566e
Bug: XWALK-637