- don't hardcode defaults in gradle files
- allow for uploading also to HTTP URLs
- support HTTP authentication when publishing

It releases the SDK and all dependencies (including React Native) to the
specified Maven repo.

When running the app from Android Studio the React packager is not automatically
started. In vanilla RN projects this is done by the "react-native run-android"
command, but often times it is desired to run from Android Studio.

This fixes that by starting the packager from Gradle.

This new version comes with an updated JSC runtime, so we no longer need to
depend on the updated version ourselves.