Modify script to use the android m2repository instead of the `extras/android/support` dir by default.

Using the m2repo guarantees the version of the jar. The `extras/android/support` dir always gets the latest version. It will use that location though as a fallback dir in case the m2repo can't be found.
Merge pull request #856 from SuperJugy/androidm2reposcript

Add a script to install support library from android's m2 repository.