Gradle plugin for setting up WordPress libraries

Potential way to manage libraries via artifacts or from source.
Cleaning up dependency location
Moving gradle plugin to own project
Merge branch 'feature/modularization' into issue/1575-local-dependency-setup
Merge remote-tracking branch 'origin/issue/extract-wpcom-rest' into issue/1575-local-dependency-setup

Conflicts:
	WordPress/build.gradle
	settings.gradle
Using 1.1.0 of gradle plugin
Merge branch 'feature/modularization' into issue/1575-local-dependency-setup
add libs/ to gitignore and remove old dependency directories
add wpcomrest as a dependency since some WPAndroid parts is still directly dependent on it
Merge pull request #1593 from wordpress-mobile/issue/1575-local-dependency-setup

Gradle plugin for setting up WordPress libraries