[FEATURE] Add a unique request ID

To allow grouping of log records belonging to a certain request,
a unique id per request is needed.

Change-Id: I76e279e3ebe22fa17b1ffdf9a57c037b75680b82
Resolves: #38954
Releases: 6.0
Reviewed-on: http://review.typo3.org/12792
Reviewed-by: Fabien Udriot
Reviewed-by: Wouter Wolters
Reviewed-by: Marcus Schwemer
Reviewed-by: Steffen Müller
Tested-by: Steffen Müller
Reviewed-by: Steffen Gebert
Tested-by: Steffen Gebert