Should fix #412

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.

Ref #122

Better error message and allow the user to still connect

Ref: #102

Add HQ card option

* add multiverse id to cards.xml
* remove pictures urls from cards.xml
TBD:
* fix/clean oracle’s gui
* add support in cockatrice

Added to CardInfo object and to the oracle importer. Next step is the
card info widget.