GUI: add booster collation settings to tourney's cubes

See comments below for details about booster collation settings

...

When choosing the set(s) for a draft or sealed tournament it would be great if we could choose sets of our own creation similar to how 'Cube From Deck' allows loading a custom cube. A custom set would be a simple text file containing a list of cards and their rarity in the set. Perhaps something like this:

```
NAME: Ice Age Remastered
DESC: Custom set using cards from Ice Age, Alliances, Coldsnap, Future Sight, Modern Horizons and Kaldheim
OPTS:
include_basic_lands=false
lands=1 # if include_basic_lands is false and this is > 0, choose a land from the card list below
commons=10
uncommons=3
rare=1
mythic_ratio=7.5

CARDS:
# rarity [set:num] name
C [ME2:245] Snow-Covered Forest
C [ICE:100] Snow Devil
U [CSP:123] Sound the Call
U [MH1:194] Abominable Treefolk
...
```

When generating booster packs the rarity of the card specified in the custom set file would be used, not the rarity the card has printed on it. For example, in the custom set above the card _Sound the Call_ has been shifted up from a common to an uncommon.

Bonus effect of implementing this feature: Whenever an official 'remastered' set is completely spoiled the XMage community could implement it as a custom set while waiting for a new XMage release to include it.