Deck import/export feature must be reviewed

Looks like some services removed deck formats support (or the new one do not have it). Import deck with set info is important feature of xmage.

TODO:
* [ ] review current popular services and apps;
* [ ] find out their deck import and export features;
* [ ] compare with xmage supported formats and fix/implement missing (load from file, import from clipboard). Good solution: xmage must able to import full deck from a service and export deck to it by minimum 1 supported format.

Example:
https://www.moxfield.com/

It’s uses own text format like MTGA, but other format options ignore set info (even MTGA). So users can’t easy to import deck to xmage without info lost.


No files, tests, or entry points are named. Start by reviewing XMage's current supported deck formats and the import/export options of services such as Moxfield, then compare the formats and identify missing support for set information, file loading, and clipboard import; done means full-deck import and export works with at least one supported format.

Written by the indexing model from the issue text.