Add different compare methods for sorting

Give DeckList nodes the ability to sort based on name, price, or
number.
Allow sorting on different columns
Sort correctly when adding cards
Fix GUI glitches when adding cards to a deck

Since we no longer sort on just card names, we need to emit updates
for the parent of the card we add.
Clean up DecklistModel::addCard()

Split common functionality out of the if-else block.
Added Mac OS X build instructions.
Don't be a jerk when card database isn't usable.

Better error message and allow the user to still connect

Ref: #102
Merge pull request #106 from VanNostrand/doc

Added Mac OS X build instructions.
Merge remote-tracking branch 'origin/master' into editor-sorting-v5
Don't have decklist sort behavior rely on column order
Merge pull request #111 from Daenyth/better-invalid-db-ux

Don't be a jerk when card database isn't usable.
Update CentOS doc in user manual

Ref #109
Notify deck editor when price feature setting is changed

Ref #112
Remove testclient cmake option.

This has been obsolete a long time
Fix Q_INTERFACES warnings

Fix #88