Add option to display set code instead of icon

[rkachniarz]

Ever since the switch from set codes to set icons in list and detail views, I am having trouble identifying what set cards are from. I would like a setting to disable the symbols, as they are less useful to me than the letter codes.

[AEFeinstein]

That's reasonable, and it should be pretty simple. I'll likely get to this next time I have a block of time to work on Familiar (unless someone else gets to it first).