TYPO3 Core

[BUGFIX] Caching framework: Remove flushByTags() and findIdentifiersByTags()

- Both backend methods flushByTags() and findIdentifiersByTags() do not exist in FLOW3
- Both methods are not used in the core
- findIdentifiersByTags() is completly unused, it even does not have a frontend wrapper method, it is fully removed from backend interface, from all backends and all tests
- flushByTags() is bogus and implemented differently in different backends: Some used to delete entries only if they where tagged with all tags, some if an entry was tagged with one of the tags.
- The frontend wrapper flushByTags() is now deprecated and implemented in the abstract as a wrapper for flushByTag() iterating through the array