Migrates android-betterpickers to Gradle and extracts 3rd party library into a dependency.
Updates .gitignore and moves dependencies section for library and sample.
Fixes sourceSets structure and moves assets dir into src.main.
Adds "android.permission.VIBRATE" to library manifest.
optimises imports.
Adds lintOptions to Library.
Un-tracks useless files.
Update .gitignore
Updates .gitignore and stops tracking /build files.