Nuget packageId case sensitivity

Nuget presumes that packageId searches will be case insensitive, but our Orient/NuGet component metadata searches are case sensitive.

Symptom:

1. Define a proxy repo for nuget.org
2. Request http://localhost:8081/repository/[repo]/NUGET.CORE/2.8.5

..throws:

Caused by: java.lang.IllegalStateException: Component metadata does not exist yet
at com.google.common.base.Preconditions.checkState(Preconditions.java:173) [na:na]
at com.sonatype.nexus.repository.nuget.internal.NugetGalleryFacetImpl$3.execute(NugetGalleryFacetImpl.java:273) [na:na]
at org.sonatype.nexus.repository.storage.StorageFacetImpl.perform(StorageFacetImpl.java:249) [na:na]
... 92 common frames omitted

What's happening is:
1. proxy facet looks for the component by the passed-in package id, 'NUGET.CORE'.
2. It find nothing.
3. NugetProxyFacet.fetch() obtains metadata for 'NUGET.CORE' '2.8.5' - nuget.org is case insensitive, and so returns the feed entry for NuGet.Core 2.8.5, which Nexus stores.
4. Nexus then requests content for NUGET.CORE 2.8.5 - nuget.org complies, but when Nexus tries to look up component metadata to attach the content to, it fails, because it's looking up NUGET.CORE.