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 is because button elements have ```box-sizing: border-box;``` by default. The difference is 2px, the width of the borders. Increasing the width in ```em```s will only give them an equal width when a certain font-size is used. Better to set ```box-sizing: border-box;``` for all icon-only buttons.