[FEATURE] New FAL Indexer and ExtractorRegistry

A new Indexer for FAL according to the concept of the BluePrint, also
adding a new ExtractorRegistry where extensions can register their
extraction classes (implementing ExtractorInterface).

See: http://wiki.typo3.org/Blueprints/FAL-IndexerRework

Releases: 6.2
Resolves: #52841, #53599
Change-Id: I06e8d011096c88221aaf62bd0a25e681692dbfa0
Reviewed-on: https://review.typo3.org/25370
Reviewed-by: Frans Saris
Tested-by: Frans Saris
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny