Summary: Like AphrontFormToggleButtonsControl, but with mouseover counters. These counters let you know how many of each thing there are in each category, which is useful when using this control for filtering a list of things in multiple dimensions.
Test Plan: `/uiexample/view/PhabricatorCountedToggleButtonsExample/`
Reviewers: epriestley
CC: aran, Korvin
Maniphest Tasks: T2094
Differential Revision: https://secure.phabricator.com/D5118
