Re-enabling problematic groupby tests
Revert "Re-enabling problematic groupby tests"

This reverts commit e04559811cf7c76030d86568de522bf94b776634.
Implemented the Northwind tests for Redis plus some tidying up (e.g. removed
BaseClassFixture since not really using it).
Updating to make UnderlyingType a metadata property
DbContext.Add should use sync path
Format JSON documents
Target aspnet50