Git standards: Added .gitignore file + removed svn leftovers

Having a .gitignore file is considered a good practise. I've added some OS files + configuration for Android Apps from this repo https://github.com/github/gitignore/blob/master/Android.gitignoreto it.
Also removed traces of .svn folders, since I'm assuming they won't be useful if using git version control system.

This pull request supersedes #43