[FEATURE] INCLUDE_TYPOSCRIPT all files from directory (recursive)

Include all TypoScript files from a directory tree:
<INCLUDE TYPOSCRIPT: source="DIR:directorypath" extensions="ts">
This includes all files from the directory, including subdirs.
If the additional property extensions=".." is provided, only
files with these file extensions are included. This allows e.g.
to include both setup and constants from the same directory tree,
using different file extensions for each.
Order in which files are included is alphabetically, first files,
then directories.

Change-Id: Ie3ca7eea47b61326dfc1f60743051be13b8aee2f
Resolves: #34621
Releases: 6.2
Reviewed-on: https://review.typo3.org/9431
Tested-by: Sebastian Michaelsen
Reviewed-by: Ronald Klomp
Tested-by: Ronald Klomp
Reviewed-by: Rens Admiraal
Reviewed-by: Francois Suter
Tested-by: Francois Suter
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind