[CLEANUP] Cleanup ext:core/Database

* Add phpDoc to properties
* Add phpDoc to functions

Resolves: #62706
Releases: master
Change-Id: Id836e7a6e6110502769b48a7693315c42d79e28a
Reviewed-on: http://review.typo3.org/33802
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>