Add to gradle files to allow for Android Studio importing

Also add compiled jni files to the gradle build.
Remove support library from the StackBlur library

The support library is not needed for the library, only for the example
app.
Refactor blur methods (native vs java) into classes

Use a common interface BlurProcess. This allows for easy switching of
what type of blur to use.
Add renderscript blur

Implements a new BlurProcess that uses Renderscript's Intrinsic Blur
Filter to blur quickly
Update example app to support renderscript
Use the renderscript support library

The renderscript support library works back to android 2.2, instead of
only 4.2 and above.
It does not currently support ARM before v7a, and will fallback to the
NDK rendering if it cannot use renderscript
Support alpha preservation when blurring with renderscript

This just copies the alpha of the original image onto the blurred copy.
Merge pull request #6 from Dr-Emann/support-renderscript

Support renderscript