Canvas: Add properties/YAML tied to a canvas (as a whole)

[btcarpenter]

+1 for Canvas properties!

[jenspoder]

Please do this! With properties being a standard functionality now, we sorely need them for Canvasses.

[ZAWatchman]

I too am surprised that this feature is not available from the outset, and not having the cavas files visible in graph view. I also support the idea of implementing this as a meta-data-card.