Add new skins for the NumericStepper component to make the UI consistent.

bigbluebutton-client/branding/default/style/css/V2Theme.css

...g/default/style/css/org/bigbluebutton/skins/ButtonSkin.as

...yle/css/org/bigbluebutton/skins/NumericStepperDownSkin.as

...style/css/org/bigbluebutton/skins/NumericStepperUpSkin.as

...ding/default/style/css/org/bigbluebutton/skins/TabSkin.as