Fix for subqueries/navigation properties

Fix: subqueries were not receiving the "as of" sql syntax
Dependency is now on .NET Standard 2.2 (rather than .NET Core) - following same convention as MS EF Core libraries.
Some additional minor refactoring.

Ensuring that service replacement is not attempted when using external service provider

v1.0.2

Version bump for nuget

Refactoring

Merge branch 'master' of https://github.com/Adam-Langley/efcore-tempo…

…ral-query

Initial Release

v1.0

change in folder structure