Fixes #533 by using the "standard" MP4 video mime type, instead of MPEG-4 Visual
Remove "Uncategorized" if a category is selected.
"Uncategorized" is also unchecked when the user select another category.
Fixed a couple of issues with categories selection and removing.
Fixes an issue where categories were not correctly selected in the Categories Tree view. It was related to a missing escapeHTML call on the name of the categories in that view.
FredrichO/AkifH - code clean up and bug fixes.

- fixed bug in media browser where switching between blogs doesn't update the media edit fragment on phone and tablet
- fixed bug in media browser where switching between blogs to clear browser and reset the spinner
- fixed bug with endless spinner on media grid
- fixed bug when you switch blogs where you end up fetching more than 50 items
- code clean up in StatsContentProvider
FredrichO/AkifH - Put in old stats activity for beta build.
Merge branch 'master' into stats