Add TKey support to EF stores
AddIdentitySqlServer rename
Add Guid key unit test

Also require new() constraint
Add ConvertIdFrom/ToString for EF store implementations
Refactor EF tests to share common base test class
Test cleanup
Remove int bug workarounds in tests
Add string key test
Rename extension classes for EF
Remove action builder overloads
Renamed configurations to frameworks in project.json
Reacting to System.Collections versioning change