[!!!][TASK] Remove typo3/ext/README.txt and typo3/sysext/README.txt

The two README.txt files within typo3/ext and typo3/sysext do
not provide crucial information that can't be found elsewhere
and are dropped now.

As a side effect, typo3/ext folder does no longer exist
with new packages - the "global" system functionality is kept.
A .rst file hints about this missing folder.

Resolves: #67824
Releases: master
Change-Id: Idc3c408f135a8be3ee2db43e4835a1c6b39436da
Reviewed-on: http://review.typo3.org/40733


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>