Generalize color definitions

[DenSinH]

Hi all,

As of now, there is a color definition file, to be used for the WidgetColorService / NamedWidgetColors. It would be useful to be able to re-use these colors in other parts of Phoebus, such as the Alarm table (which parses, for which colors are defined as integer arrays in phoebus_ui_preferences.properties. Basically, to have some sort of 'central' (Named) ColorService.