Charts and Stats for Categories

- Browser search added
- added sidebar for fast Stats search containing the user's providers, browsers and categories
- the general Stats are adaptive to the search (e.g. 'avg. duration' is hidden if there's only one video)
- streamlined Stats JS
- show "All videos" only when appropriate
- the Provider Line graph is widened if possible
- graphs are only rendered when meaningful
- Log and Stats can be toggled