[TASK] Cleanup RTE HTMLArea TSconfig processing options

Some obsolete options are found in the documentation, additionally
the RTE.default.proc.exitHTMLparser_db is not enabled by default
anymore, as the functionality to keep non matched tags is not needed.

In case of a site extending the default exitHTMLparser_db configuration of
HTMLArea, it has to be enabled like this:

	RTE.default.proc.exitHTMLparser_db = 1
	RTE.default.proc.exitHTMLparser_db {
			## KEEP ALL TAGS
			## Unwanted tags were removed on entry.
			## Without this rule, the parser will remove all tags! Presumably, this rule will be more efficient than repeating the allowTags rule
		keepNonMatchedTags = 1
	}

Resolves: #79346
Releases: master
Change-Id: Ie7208a3fc751b2b712ec773a148c4404965abd99
Reviewed-on: https://review.typo3.org/51299


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>