[Enh]: Package Maps - Spawn RPackage if Loaded

[seandenigris]

... or package spec otherwise

Before:

• When clicking on nodes representing loaded artifacts, the behavior is not consistent. For baseline nodes (e.g. PharoEnhancements in the screencast), the baseline class is spawned, but for package nodes (e.g. Magritte-Money in screencast), the package spec is spawned, not the package itself.
• When clicking on a node representing an unloaded baseline (Seaside3 in screencast), an error occurs.

before.mp4

After:

• When clicking on a loaded package's node, spawn the package
• When clicking on an unloaded baseline node, spawn the spec.

after.mp4