Improve debugger support on Android

[tbuschto]

Android JS debugging is currently not a great experience. The following improvements would be essential:

• Fix https://github.com/eclipsesource/tabris-js/issues/1690
• Fix https://github.com/eclipsesource/tabris-js/issues/1691

Of secondary priority:

• Allow debugging with store developer app.
• Allow adding Watch Expressions.
• Support source maps for TypeScript support.
• Allow exploring the JS widget tree instead of/in addition to the native tree.

[tbuschto]

@mpost @irbull Any input?