Improve "write block" key selection behavior

[ikarus23]

When using "Write Block" from the "Write Tag" menu, MCT will first try to write with key B and if this fails with key A. This not the fastest but it is ok for original cards.

However, there are gen2 and gen3 tags out there which report a write success, although it failed due to authentication with the wrong key.

The improved "Write Block" process should read the access conditions of the target sector and determine the correct write key instead of just trying.