CMS-3189 Make Button's/ActionButton's glow slightly when focused

- added Tab handling to TextSearchField
- fixed button hierarchy api.dom.ButtonEl -> api.ui.Button -> api.ui.ActionButton -> api.ui.DialogButton
- created base button.less class applied to all api.ui.Button's
- refactored all .less buttons declarations
- added button.less to live edit
- increased padding for form view add button