Added Checksum Collection and Rebuild Task
Added Update Detection
Got each piece of the incremental update pipeline working!
Added deletion support
Moved Catalog Maintenance code to a separate class
Restructured Constants file and moved predicate URLs to schema.nuget.org
Added some more data to the catalog
Finished incremental catalog update logic
Merge branch 'master' into anurse/incrementalcatalogupdate

Conflicts:
	src/Catalog/Collecting/Collector.cs
	src/Catalog/Constants.cs
	src/Catalog/GalleryIntegration/GalleryKeyCollector.cs
	src/Catalog/Maintenance/CatalogContainer.cs
	src/Catalog/Maintenance/PackageCatalogItem.cs
	src/Catalog/context/Container.json
	src/Catalog/context/Resolver.json
	src/Catalog/sparql/ConstructResolverGraph.rq
	tests/CatalogTests/CollectorTests.cs
	tests/CatalogTests/End2EndTests.cs
	tests/CatalogTests/ExportTests.cs
Changed URIs to use fragments
Fixed up SPARQL
Fixed some build issues and restored tests project
Merge pull request #4 from NuGet/anurse/incrementalcatalogupdate

Added incremental catalog updating