Refactoring styling for ContextualPopupButton and Button…

…to handle overrides more cleanly and support easier customization.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)
Merge branch 'contextual-popup-button-cleanup-graynorton'
BHV-3377 Contextual Popup Button: Add grey arrow to deactivated state Enyo-DCO-1.1-Signed-off-by: Brooke Peterson <brooke.peterson@lge.com>
Merge pull request #1213 from enyojs/BHV-3377-brookepeterson

Bhv 3377 brookepeterson

Reviewed-By: Cole Davis (cole.davis@lge.com)