Summary:
Adding a way to install plugins directly from package files. This is required for testing after packaging format changes.
Stage 3: Implemented installation of plugins directly from package file.
Reviewed By: jknoxville
Differential Revision: D19765619
fbshipit-source-id: 57f36c87d3cf5d4e1c9a1f8f9f9f32b14a18bc8b
