Bok-Choy CMS Video Tests

Bok-Choy tests for [video.feature](https://github.com/edx/edx-platform/blob/master/cms/djangoapps/contentstore/features/video.feature)

@auraz @polesye @jzoldak 
> Actually these checks are related to page object and should be in a page object class. Please suggest what can be moved to CMSVideoTest._create_video

As for me it looks like a part of the test and this method is used just once. I think we can move everything after line `self.wait_for_video_component_render()`