Add the ability to lock assets.
ui changes from design team feedback on studio assets page
Update upload test for what actually works now.
addressing PR sass/html comments on studio assets
Asset locking feature.
Code review feedback.
Delete asset from cache.
switching studio assets lock to use checkbox instead of link
Updates based on switching to checkbox for locking.
Merge pull request #1069 from edx/christina/lock-assets

Add asset locking to the Studio asset page.