[Android] Display no scaled image when no border specified in LaunchScreen

When no border specified in the manifest, the image should not be scaled, just display
the image centered in the screen.

BUG=XWALK-1998
[Tizen][Runtime] Fix allow-navigation element can not take effect if there are more than 1 in config.xml.

In Tizen core spec, it's said that "if more than 1, the first occurrence MUST be considered (and all others
ignored)." This patch makes the runtime following the spec.

BUG=XWALK-1696
Merge pull request #2133 from kurli/launch_screen_image_fix

[Android] Display no scaled image when no border specified in LaunchScreen
Merge pull request #2143 from takethathe/fix-duplicate-element

[Tizen][Runtime] Fix allow-navigation element can not take effect if there are more than 1 tags in config.xml
[Android] Support http://w3c.github.io/manifest/ for packaging tool

Support "start_url", "xwalk_launch_screen" and 'xwalk_permissions' field in manifest.
The legacy field "app.launch.local_path", "launch_screen" and 'permissions'
are still supported, but will print a warning message.