Updated the projects and the corresponding references to .NET core 2.0

[ankobi]

Hi,

I really like your project and appreciate the work you already put into this. Unfortunately I could not use it in my current project due to the fact that this lib is not yet based on .NET core 2.0 and unfortunately it is also not compatible. This is because the guys from Microsoft i.e. moved the DeleteBehavior to another namespace.
I updated the project, maybe this was also on your agenda. If you plan to update, please feel free to get the changes from my fork.

[EvAlex]

Hi

Wow, that's a breaking change indeed. Thank you for your contribution! I'm thinking what to do now. Projects using asp.net core below 2.0 will break if I merge this, but newer projects need this.

[bruce-willis]

@EvAlex I'm also very appreciated for work you've already done. Now .Net Core 2.0 is in release version more than 3 months, so, I think, it's time to update package to this version. I add to README in my fork reference for version 0.4.2, which should take who wants to create a project at .Net Core 1.1.