Integrate AddReferenceInFSI to VFPT

Close #897.

This is a faithful port of AddReferenceInFSI to VFPT.

I list here a few possible improvements for discussion:

 1. The menu item only appears in `References` nodes in Solution Explorer. Should we display it when right click on Projects as well?

 2. The feature generates references for all configurations in current project. Is this really neccessary? Should we change to generate references for active configuration only?

 3. A few known assemblies are generated using full paths (see below).  Perhaps we should use assembly names only?

    ```fsharp
#r @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.dll"
#r @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Core.dll"
#r @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Numerics.dll"
     ```
 4. **Any other ideas you have in order to improve this feature.**


/cc @vasily-kirichenko @OkayX6 @halcwb 

minor: FSI or Fsi? :)