Filter out invalid cards when building deck. (#568)
Filter out invalid cards when building deck. (#568)

Previously, it was possible to end up with agendas in the draw deck.
These and other non-draw cards are now filtered out when the deck is
constructed at the start of a game.

Resolves https://sentry.io/throneteki/throneteki/issues/232365876/
samuellinde/throneteki,jbrz/throneteki,jeremylarner/ringteki,DukeTax/throneteki,Antaiseito/throneteki_for_doomtown,cryogen/throneteki,cryogen/throneteki,gryffon/ringteki,jeremylarner/ringteki,jeremylarner/ringteki,cryogen/gameteki,jbrz/throneteki,cryogen/gameteki,samuellinde/throneteki,gryffon/ringteki,DukeTax/throneteki,gryffon/ringteki,Antaiseito/throneteki_for_doomtown,ystros/throneteki