[TASK] impexp: Use XML as default export format

The TYPO3 specific .t3d export format is a funny binary format
and rather hard to read and decipher, even if not compressed.
The XML format is at least some easy to read text file instead
of a binary format and exists for quite some time in the system.
Use XML as default export format by just swapping the option
box entries.

Change-Id: I5b25d8dc0b33158e98d1aafba27ab7669edeb725
Resolves: #83597
Releases: master
Reviewed-on: https://review.typo3.org/55383


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Reiner Teubner <rteubner@me.com>
Tested-by: Reiner Teubner <rteubner@me.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>