3627 android content insets

[lgeromegnace]

This PR is meant to implement padding functionality on android platform described in this issue #3627.

• Add a setPaddingContent method on MapView
• Padding are stored in NativeMapView to be applied on any methods that can update current bounding box.

[tobrun]

@lgeromegnace this is great, will review soon!

[bleege]

This looks like a great start to the API. I just rebased and merged it into master. We'll still need to have this work with the Camera API and build an example in the TestApp.

Thanks for the contribution @lgeromegnace!