Clean up migration area of .NET guidance

[adegeo]

The migration/porting information has a lot of irrelevant information, such as migrating from DNX (RC1 of 1.0) to .NET CLI (RC2 of 1.0). All of this old information should be deleted and/or brought up-to-date.

This issue is here to track that effort.

Migration guide

• Migration

  • .NET Core 2.0 to 2.1 (DELETE but move <DotNetCliToolReference> info to the Breaking Changes 2.1 article) (Add breaking change from 2.0-2.1 #22917)
  • Migrate from project.json (DELETE project.json/.xproj/DNX material hasn't applied for years.) (Remove DNX content #22919)
  • Map between project.json and csproj (DELETE) (Remove DNX content #22919)
  • Map AssemblyInfo attributes to properties (MOVE to the MSBuild info area) (Move the assembly property information to the msbuild info article #22918)
  • Changes in CLI overview (DELETE conceptual material describing pre .NET Core 1 world) (Remove DNX content #22919)
  • Migrate from DNX (DELETE DNX material hasn't applied for years) (Remove DNX content #22919)

• Port from .NET Framework

  • Overview (UPDATE/SPLIT Article isn't really an overview. Lots of information, some steps to follow too, article has a mixed identity) (migration article work #23218)
  • Analyze third-party dependencies (UPDATE Need better intro and flow)
  • Port libraries (UPDATE Good information, should be pointed to by other articles such as port WPF) (migration article work #23218)
  • Organize projects for .NET (INVESTIGATE Describes code sharing. Probably more useful back when WinForms/WPF wasn't available. Not sure how relevant this is anymore) (migration article work #23218)
  • Unavailable technologies (KEEP) (migration article work #23218)
  • Tools (DELETE Too small. Move content to the overview article) (migration article work #23218)
  • Use the Windows Compatibility Pack (UPDATE Good information, should be pointed to by other articles such as port WPF) (migration article work #23218)
  • Port Windows Forms projects (KEEP) (migration article work #23218)
  • Port WPF projects (KEEP Link is redirecting, fix) (migration article work #23218)
  • Port C++/CLI projects (KEEP) (migration article work #23218)

Possible future

• Reference MSBuild Assembly Info attribute section in future content
• File issue for MSBuild Assembly Info section to break out all of the individual settings