Portals don't have their dedicated context menu options, such as revert all to wires

Steps to reproduce:

1. Create and open a graph
2. Add two nodes and connect their input and output ports to each other
3. Right-click on the wire and create a portal
4. Right-click on the portals

Actual results: The portal specific context menu items are not there

Expected results: Portal specific context menu items are displayed, as shown in the image below

Reproducible with versions: 0.4.0

Not reproducible with versions: 0.3.0

Tested on (OS): MacOS