Button Re-write

This replaces PR #1216 

This includes new widget controlgroup which replaces buttonset
Current known issues 
 - [x] 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
 - [x] Controlgroup icon only buttons 1px too short in chrome, firefox extra weird @jaspermdegroot think you could take a look?
 - [x] demos/controlgroup/default.html As above, labels should demo something
 - [x] 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 is an improvement and more demo-like. Though as-is a bit irritating: It looks like its a part of a rating UI, where it wouldn't make sense to select multiple ratings. Maybe change the legend to "Filter by rating"?

As for the markup, shouldn't they all share the same name and have a value attribute? Maybe use "rating" instead of "checkbox"?