Delve: Exclude faction troops from colour restrictions

Well, we narrowly avoided a repetition of the Occularen trouble. Won’t be the last time; it’s a long stretch between delve weekends, long enough to forget about this factor, and when balancing out the colours and trying not to create duplicate mixes, it’s easy to accidentially end up with a troop, that is outside the requirements.

A possible solution, that was suggested when the Eye issue was ongoing, would be to simply add “faction troop” as an additional qualifier for delve participation, even when the colours are not among the required ones.
Would save work and headaches in the long run.