Mojo: Rename ServiceManager to ApplicationManager.

Also, ServiceLoader->ApplicationLoader, and all related implementations.

TBR=timurrrr@chromium.org

Review URL: https://codereview.chromium.org/455993002

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@288594 4ff67af0-8c30-449e-8e8b-ad334ec8d88c