GitLab

Adds Glide, an image loading library, to handle image caching and bitmap reuse.
This is working, but there are still some significant todos:

1. We're loading larger images than we need.
2. We're not aggressively cancelling loads so if you scroll far
  it takes longer than necessary for the image to appear.
3. Video thumbnail loading is slow (will require changes to Glide to improve).

Change-Id: I01387429068451b923509f78c6d5f8ce115e74ad