"Open Containing Folder" does not work for project references/analyzers

## Visual Studio Version
17.14

## Summary

## Steps to Reproduce

1. Create 2 x .NET Core projects
2. Drag one onto the other to add a reference
3. In Dependencies expand to that project, right-click and choose Open Containing Folder

## Expected Behavior
To open the containing folder

## Actual Behavior
Does not

## User Impact

Dave is sad because he wrote this feature.

The same applies to analyzers.