[BUGFIX] LocalDriver: Recursive file listing is broken

The recursive file listing, introduced as part of the public API in
the fix for #43249, is currently broken.

One problem is that the file information retrieval is incomplete: The
filename of files in subfolders also contains the path to this file from
the current folder, while the identifier is missing that information.
The identifier is thus wrong and the filename contains too much
information (more than the filename).

Additionally, the method getDirectoryItemList() returns the file list
with the filenames as key, which will fail when a file name exists twice
in different folders. Therefore, this patch changes the keys to numeric
values when a recursive folder list is requested.

Change-Id: Iaebd862327d2dfc849044236474f6da2444cd4f5
Resolves: #44910
Releases: 6.2, 6.1, 6.0
Reviewed-on: https://review.typo3.org/22193
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
[BUGFIX] FAL: Image Processing doesn't respect GFX "thumbnails_png"

The Task Interface of the File Abstraction Layer defines the
target file extension for graphcal tasks. Previously this was done
with the option "thumbnails_png" from the TYPO3_CONF_VARS.

However, checking for that parameter is not done anymore within
FAL/AbstractGraphicalTask. Thus, all .gif images are shown as .png
files, even though TYPO3 is not configured like that.

This can be seen when using GM, thumbnails_png=0, and creating
a preview image of an animated GIF. The preview will not be shown
for some images then.

The patch introduces the existing option back in to 6.x/FAL.

Releases: 6.2, 6.1, 6.0
Resolves: #50193
Change-Id: Ie539fe1aa1ab7366129a156be8ce9b05a5f8d5d2
Reviewed-on: https://review.typo3.org/22850
Reviewed-by: Anja Leichsenring
Tested-by: Marc Fell
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters