Move the package to the official Nuget feed

[fleed]

The package should be accessible from the official NuGet repository.

[crhairr]

When there is an actual release, absolutely. Now that 2.1 is officially out and out of rtm, I can create a release branch and push packages to NuGet.org.

I'm still in the process of working through an issue with complex types and mapping them onto EFCore's terrible, SQL-centric "owned types" metadata system. Once that gets complete, EFCore-MongoDB should be ready for an actual release.