Consolidate all EF document sets currently in other repos like .NET Framework docs

I ran into this old document sets that have been ported:

- https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/ef/overview
- https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/entity-data-model
- https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/ef/language-reference/index
https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/association-set (From
https://github.com/dotnet/docs/blob/master/docs/framework/data/adonet/association-set.md)
- https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/navigation-property

And others that apparently haven't been ported: -
- [ADO.NET Entity Framework](https://msdn.microsoft.com/library/bb399572(v=vs.90).aspx) using Microsoft SQL Server 2005 and Visual Studio 2008. Duplicate of the following version. ***Recommend not porting this.***
- [ADO.NET Entity Framework ](https://msdn.microsoft.com/library/bb399572(v=vs.100).aspx) With VS 2010 redirects to https://docs.microsoft.com/previous-versions/dotnet/netframework-4.0/bb399572(v%3dvs.100)
- [ADO.NET Entity Data Model Tools](https://msdn.microsoft.com/library/91076853-0881-421b-837a-f582f36be527) **7 Topics below this. I'm guessing they should all be moved.**
- https://msdn.microsoft.com/library/f4c8e7ce-1db6-417e-9759-15f8b55155d4
- https://msdn.microsoft.com/library/cc835494(v=sql.105).aspx
- https://msdn.microsoft.com/library/bb896240.aspx
- https://msdn.microsoft.com/library/cc716700.aspx (remove usage of word "might")
- https://docs.microsoft.com/previous-versions/bb399600(v=vs.90) (see https://github.com/dotnet/dotnet-api-docs/issues/1287)

Would probably make sense to merge anything that that has value into the EF6 docs, redirect and remove them.

I believe this one was supposed to be part of the migration of EF6 contents but it doesn't show up in the PR:
- https://msdn.microsoft.com/en-us/library/gg696172(v=vs.103).aspx (assetid: 87d022ee-c4bf-4118-8034-51c8510c31d0).