Button Re-write

This replaces PR #1216 

This includes new widget controlgroup which replaces buttonset
Current known issues 
 - [ ] Accordion Test Failures due to focus not working in phantom
 - [ ] Checkboxradio testfailure missing default element (@scott_gonzalez said it should not have one because it cant be sane ) this causes common tests to fail
 - [ ] Backcompat
 - [ ] Controlgroup icon only buttons 1px too short in chrome, firefox extra weird @jaspermdegroot think you could take a look?
 - [ ] demos/controlgroup/default.html As above, labels should demo something
 - [ ] demos/checkboxradio/default.html doesn't have the "command line" anymore, but still doesn't look like a demo. Labels should reflect some real world usecase.
 - [ ] demos/button/icons.html still looks like a visual test, not a demo

This example looks awful. Having a very wide button with a single icon is not good enough for a demo. Can we bring back the [toolbar demo](http://view.jqueryui.com/1.11.1/demos/button/toolbar.html)? Maybe also [splitbutton](http://view.jqueryui.com/1.11.1/demos/button/splitbutton.html)?