[BUGFIX] Implement EXT: usage in addModule

Make it possible to use EXT: for resolving paths in addModule

Resolves: #68341
Releases: master, 6.2
Change-Id: Ic26d410f09303baa4fa18c744b30ee72ada09227
Reviewed-on: http://review.typo3.org/41667


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>