Clean up code leftovers
Sets: case insensitive sorting
Strip { } around mana cost
Rename the finish/done button as "Save"
Add an option to force selection of save path

By default oracle saves cards.xml to the correct path, where cockatrice
will be able to pick it up;
if oracle is not able to determine the path or the user unchecks the
option, oracle will ask for a save path
Don't lock the UI if the loaded file was not readable