Removed the QLists for determining image format. Instead, using QImageReader, both when downloading/saving and when loading, to determine the correct format (Cockatrice now supports all QImageReader-supported formats).
Image loading still uses one for loop to iterate through the QList of paths to folders in which to search for images.

Refactored the magic bytes into two QLists: one containing a list of QStrings representing the supported extensions, the other containing a list of QByteArrays representing the magic bytes in hex.
Refactored the image loading loop to be two nested for loops: the outer loop iterating through the QList of paths to folders in which to search for images and the inner loop iterating through the QList of supported extensions.

Switched back to using QFile instead of QImage for saving as QImage's save function adds overhead to the file size, leaving me unsure whether the original image is affected.

Added better support for custom card images

Add back support for custom picture urls in cards.xml

Disable some usercontextmenu actions if the user is offline; fix #234

Fix building with debug

Fix #110: Price column is removed when the setting is disabled.

Fix issue mentioned in #152: price updater loads all cards now.

Using pointers for classes derived from QObject would be the best idea.

Add pricing from deckbrew.com (refs #147)

Fix #225: Multiples of cards are now sent to deckstats.

Fix #183: Deck parser doesn't too eagerly replace ampersands.

Fix #45: don't send tokens to deckstats.

Æ now actually works with the case-insensitive tags.

Conflicts:
	cockatrice/src/carddatabase.cpp