Update and fix build files and project dependencies

This PR
- updates the project to the latest target sdk version
- fixes Maven build problems (android jars for sdk 17+ are not available from Maven Central anymore, so they need to be deployed locally)
- updates the ActionBarSherlock reference from 4.3.1 to 4.4.0
- updates android-maven-plugin reference from 3.6.0 to 3.8.0 (note that Maven 3.1.1+ is required)
- updates a few version numbers that were missed
- adds proper .gitignore files and adds project.properties files which fixes the incorrect sdk level selection after importing