* Registered video MIME types
* Currently supporting browser-supported formats with extensions that match the mime type

This attempts to get CarrierWave's uploader - `FileUploader` into test
harness using a factory. that makes it easier to build an instance of
it.

Along with !3435 it may be easier to use uploaders in tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This commit generalizes the image upload via drag and drop so it supports all files.
It also adds access control for these files.