Consider moving to Microsoft.Extensions.FeatureManagement

[TheBlueSky]

Consider changing the namespaces and the assembly name to be Microsoft.Extensions.FeatureManagement. IMO, this makes the library look more like the rest of .NET Core "standard" libraries than a stand-alone thing.

Besides, it has the same "spirit" that other Microsoft.Extensions.* libraries have.

[jimmyca15]

Thanks for the feedback @TheBlueSky. This is something the team considered early on and it turned out extensions is not the best namespace for this project. It's a good proposal though, just didn't seem to fit.