Change ConfigurationPolicy of all EntityDereferencer and EntitySearcher ComponentFactories to OPTIONAL

All EntityDereferencer and EntitySearcher implementations (all of them in the entityhub.site.linkeddata module) have used ConfigurationPolicy.REQUIRE since the beginning. The idea was that instances created with this ComponentFactories do require a configuration. However that is not the intention of the annotation. The annotation defines if the factory needs a configuration. As this is not required the correct annotation is ConfigurationPolicy.OPTIONAL.

Before STANBOL-1322 this was not an issue as the used Felix version had ignored the configuration policy for ComponentFactories. However after the version update this is no longer the case and the therefore no ComponentFactories for EntityDereferencer and EntitySearcher where created.

Because of that no Entityhub ReferencedSite with configured EntitySearcher or EntityDereferencer could be created.

To Solve this one needs to changte the ConfigurationPolicy annotation of all
EntityDereferencer and EntitySearcher implementations from REQUIRE to OPTIONAL (the default).

NOTE: the 1.0.0-SNAPSHOT is not affected by that as part of STANBOL-1127 in r1539617