Support .NET Core, as well as .NET Framework

[tsahi]

Is your feature request related to a problem? Please describe.
Enterprise Library as a whole, and DAAB in particular, were last released in 2013, long before .NET Core was released. As .NET Core is the future of .NET, we should support it. At the same time, .NET Framework is still widely used, and we want any new features to be available to .NET Framework as well.

Describe the solution you'd like
We should refactor the code to a Shared Project, and consume it from a .NET Core and a .NET Framework projects, with the necessary technique (e.g. DI) to accommodate for the differences.

Describe alternatives you've considered
There is a port of EntLib to .NET Core https://github.com/EnterpriseLibrary/data-access-application-block, but it didn't add any new functionality. We may work with them though.

• Discussion on this topic is done on Support .NET Core, as well as .NET Framework data-access-application-block#5

[tsahi]

The Common block's main function is to provide wrappers around the System.Configuration namespace. But this namespace doesn't exist in .NET Core. Instead, there is the IConfiguration interface, which is much simpler, and might not need any wrappers around it. It could be that in the .NET Core version of the blocks there won't be a dependency on Common, and only the .NET Framework will use it.