This way injects will be resolved inside of processors, enabling
developers to inject dependencies.
We use inject instead of constructor as indexers mostly will change the
constructor and should not need to add the objectmanager.
Resolves: #117
Before data processing was applied for TCA only, through tca table
service.
Now it's applied much later in process and in abstract indexer.
Therefore all indexer will run data processing if configured.
Ad TYPO3 Core now makes use of Doctrine, a connection is required to
build system where. Therefore we move it to an own method to exchange
the execution inside of tests.