Theming: Unify namings

The names for Color[Role] and Gradient[Stop] are not used consistently.
This patch unfifies the naming.

Change-Id: Idd06978a628427cb448a158d620bea561752750d
Reviewed-by: hjk <hjk121@nokiamail.com>
Theming: WelcomeScreen fixes

Restores the separation line in the WelcomeScreen
Some colors were still referenced with the incorrect name.

Change-Id: Ia0de1b4779ecc67030ebb4a5877edd5a6f24085c
Reviewed-by: hjk <hjk121@nokiamail.com>