* main.cpp: removed path checking and db loading
 * card database: merge card loading methods into a single one
 * settings cache: take care of returning safe paths for decks,
replays, etc..
 * main window: if db loading fails (eg. first run), propose to run
oracle

NSIS: propose to run cockatrice instead of oracle

Rework card database loading

 * Move carddatabase-related method out of deckeditor tab
 * Load cards in another thread and render them progressively
 * Optimize database reload after enabled sets change

Fix deck editor column width

 * removed the noCard hack.
 * getCard() no more creates cards instead of just returning existing
ones
 * Fix the “edit tokens” dialog.
 * PictureLoader: avoid trying to download twice the same card
 * PictureLoader: correct return of card background
 * AbstractCardItem: avoid recalculating card color at every paint

Use a different file to save custom tokens

Misc required improvements

 * Use nullptr;
 * Refactor CardInfoWidget to use CardInfoPicture and CardInfoText
instead of duplicating code;
 * Added CardInfo::getColorChar()
 * Fixed some potential crashes
 * removed dead code related to CardInfoWidget
 * Don't require a restart after adding a new custom sets file
 * Bump CMake requirements to 3.1

 * Use the new, shortest API m=
 * for a card, grab prices for all sets
 * use the lower price for a card from all sets, but avoid prices=0
(e.g.: some M15 cards have no price yet)

Query card database to get a multiverseis for a card.
Get card price using that id instead of card name.
Tested Aether, split cards, question elemental?, _____

* the previous PriceUpdater class has become abstract
* BLPPriceUpdater inherits the old code for blacklotusproject.com
* DBPriceUpdater is a new implementation for deckbrew.com
* add a setting to choose between the two

Ref #112

"The price tag feature currently has two bugs.
1. The final price that a card ends up with is the one in the last set
alphabetically, instead of the one from the set with the lowest price.
2. Black Lotus Project sometimes gets in prices for cards from Masters
Edition, for some reason. This set only exists in Magic the Gathering:
Online, i.e., not physically, and should not be considered. This might
be considered a BLP bug and not a Cockatrice bug.

This patch fixes those two bugs. I also changed the price value to be
based on BLP's "price" value instead of the "average" value. Seems more
logical."

Signed-off-by: Daenyth <Daenyth+git@gmail.com>

Converted PriceUpdater from QScriptEngine to Qt-Json. I don't feel comfortable running unchecked JS code from an external source.

price is dispay in both places.