EventLogging: break up MobileWebClickTracking

The MobileWebClickTracking table is getting huge. Splitting it into
several schemas will make it easier to manage.

The new schemas are:
* MobileWebWatchlistClickTracking
* MobileWebDiffClickTracking
* MobileWebMainMenuClickTracking
* MobileWebUIClickTracking

Change-Id: I623fde482baaba753608160d486d79a313ee5825
Merge "EventLogging: break up MobileWebClickTracking"