Allow using theme colors as label/value colors

[alltime84]

Hi!
For the Android Client primary and secondary will be added to the the list of known colors.
So that the theme-colors can be used as label or value color as well.
openhab/openhab-android#3248

Maybe this would be an idea for the iOS app as well? Or at least to check that this option is not causing any issue for the iOS app?

Thanks!
Tim