Extract Common Library into Independent Nuget Package

[theczorn]

We need to extract out the Common library into a standalone package.

The idea being that this is a stepping stone to more dynamic configuration within Blackslope. Once we've spun the Common package out we can begin extracting subsets of functionality from it into their own Nuget packages.

Ultimately, we can use this structure to extract out "opinionated" tooling from our Common package until only the most basic functionality resides (or the Common project is deprecated/absorbed entirely). These opinionated packages can then be plug-and-played into the Blackslope project for rapid configuration/deploy.

e.g. - a package for Serilog vs Nlog, etc.

This will cause breakages, notably in the VersionService.

[stephenweinrich]

We should create nuspec files for each package we create so that there is an option to host versioned artifacts in a nuget repo.