Prepare gradle for two versions

This PR requires Android Studio 0.9+

If you want to build all releases from gradle:
1. create file release.properties in ../ with content:
  keyStorePassword=YourPassword
  keyAliasPassword=YourPassword
in terminal run
gradlew assembleRelease
question: each flavor require a unique version code, right ?
so every new release will be a version bump by 2