Add Logging category names to ConfigurationSchema

[eerhardt]

This allows for auto completion and intellisense for the Logging:LogLevel section of the appsettings.json file.

Fix #174

[eerhardt]

These changes were all sorting and deduping.

[DamianEdwards]

@eerhardt screenshot of the result in VS?

[eerhardt]

@eerhardt screenshot of the result in VS?

and finally:

(note the green squiggly goes away once you pick a value:

[DamianEdwards]

Awesome! This leads to another potential feature request for the dynamic schema feature, namely being able to request that the properties being added can be expanded via a configurable character (in this case .), so that Microsoft.Extensions.Caching.StackExchangeRedis gets expanded to Microsoft, Microsoft.Extensions, Microsoft.Extensions.Caching and Microsoft.Extensions.Caching.StackExchangeRedis. It's similar to the hierarchical expansion for contributed sections we've discussed, but for properties instead.