[TYPO3-mvc] RFC #11978: Clearing the whole page cache using Tx_Extbase_Utility_Cache::clearPageCache() is "impossible"

[Felix Oertel]

FYI: I committed a follow-up to trunk r3912 because of a missed type-hint.

I also took Björn Steinbrink's notes [1] into account. I also changed 
the empty DELETEquery to be a TRUNCATEquery.

regards, foertel