[FEATURE] Add clearing cache by tag and by identifier clearCacheCMD

The caching framework supports to remove cache entries by identifier
and by id. If this was supported by the t3lib_tcemain->clear_cacheCmd(),
this feature could also be used in TSConfig's TCEMAIN.clearCacheCmd.

As both require an additional parameter I suggest a syntax like this:

TCEMAIN.clearCacheCmd = cacheTag:firsttag,cacheTag:secondtag
TCEMAIN.clearCacheCmd = cacheId:first,cacheId:anotherid

Change-Id: Ib0936aa9c0f50dc26ebd78417a29b1582d078b46
Fixes: #34352
Releases: 4.7
Reviewed-on: http://review.typo3.org/9266
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch