Gradle Default Properties Renamed

Renamed a few properties to make things more consistent:

BuildType.runProguard -> minifyEnabled
BuildType.zipAlign -> zipAlignEnabled
BuildType.jniDebugBuild -> jniDebuggable
BuildType.renderscriptDebug -> renderscriptDebuggable
ProductFlavor.renderscriptSupportMode -> renderscriptSupportModeEnabled
ProductFlavor.renderscriptNdkMode -> renderscriptNdkModeEnabled