WOBS-700: Optimize ingest memory usage

Remove Feed-Entity relation.

Conflicts:
	newscoop/library/Newscoop/Services/IngestService.php
	newscoop/tests/library/Newscoop/Services/Ingest/PublisherServiceTest.php
	newscoop/tests/library/Newscoop/Services/IngestServiceTest.php
WOBS-700: Optimize ingest memory usage

Fix tests.
Merge branch 'optimize-ingest-41' of https://github.com/petrjasek/Newscoop into v4.1