[TASK] EM: Improve appearance of "get extensions"

* Change order of table-heads to reflect scribble better
* Include link to all version of extensions as arrow
* Move details of author into description and hide for now
* Move loading mask on extension table

Resolves: #42327
Releases: 6.0

Change-Id: I9e042f972a77e09482a5eeab429214bb13108f71
Reviewed-on: http://review.typo3.org/15916
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel