SPARQLStore / Use FixedInMemoryCache in RedirectLookup

Use the `FixedInMemoryCache` instead of an open array to avoid any
potential memory leak.
SPARQLStore check for non-redirectable resources in RedirectLookup

Reduce query requests to the RDF Store for only resources that can have
a redirect and avoid resource drain on elements such as 'rdf, 'rdfs' etc.
Merge pull request #600 from SemanticMediaWiki/sparql-redirectlookup

SPARQLStore RedirectLookup check for non-redirectable resources