[TASK] Move documentation to reST

Move documentation to reStructuredText.
Removed old documentation.

Resolves: #57774
Releases: 1.5
Change-Id: Ife2c5d139f83ac56634a85237b7f8e14d203aa7b
Reviewed-on: https://review.typo3.org/29320
Reviewed-by: Francois Suter
Tested-by: Francois Suter