Added generators for DataSet and DataTable types (both typed and vanilla)

[logiclrd]

This PR:

• Adds generator types DataSetGenerator and DataTableGenerator. These contain code both for vanillaDataSetandDataTableand for typedDataSetandDataTable` objects.
• Updates AutoGeneratorFactory.ResolveGenerator to tie these in for the types they support.
• Adds necessary references to the projects in the solution. In AutoBogus.csproj, a regular reference to the system library is used for the net40 build target framework, a package reference is used for the netstandard2.0 target framework, and the code is #ifed out for the netstandard1.3 target framework.
• Adds unit tests for the new functionality.
• Fixes a bug in AutoBogus.Tests.NET45.csproj that was preventing it from running tests successfully. Its packages.config referenced xunit.runner.visualstudio version 2.4.1, but for some reason the .csproj had <Import> and <Error> lines referencing version 2.4.3 of that package, which did not exist in my packages cache folder.

The net result of this should be that AutoFaker.Generate<MyDataTableType>() should be able to create an instance of the typed DataTable and populate it with bogus data. I would like to use AutoBogus in a context where there are a bunch of auto-generated typed DataTable types.

[logiclrd]

@nickdodd79 If there's a chance you might merge this in, just not before EOD today, would you consider marking this PR with the label hacktoberfest-accepted? :-)

[nickdodd79]

Hey @logiclrd

Thanks for the contribution. Hopefully I tagged it correctly.

Nick.