Pull all of the colours out into the resources

[sebheron]

I'm thinking we should take all the colours and put them into a separate resources file.
My thinking is we can then work on adding in dark mode theming, hacker theming, halo theming, heretic theme?
Maybe this is even an opportunity to add the ability to customize themes yourself and export them, and import other peoples themes.
I've split this up for now into 2 Issues as I don't know how long it'd take. I thought I could take the brunt and do this issue, compiling all the colours into a resource and then you could take other work of implementing a colour themer thingy if you fancy it? Think it will be some interesting work.

[aidanhorton]

Feel free to do both! I've got other things I can pick up if you fancy doing it 😉
At the very least the colours need to be extracted away from each separate control and into some form of centralized system - I guess we can leave it with whoever implements this to decide the way they want to architect it - I don't think you can really go wrong with any method here.

Approved!