dashboardv3 should use connector icons from registry

[quartzjer]

every connector should have it's official icon.png in the registry and that should be used by dashboardv3. The Ops/registry.js should cache and serve these locally...

[quartzjer]

I think this is a simple change to use this as a base https://burrow.singly.com/registry/twitter/icon.png wherever the local icons are referenced, and enforce fixed sizes on the images (just in case icon.png isn't)... but it's lost on me how the common/template stuff works where I see references to it.

I don't think it's critical for USEIT so I'm changing the milestone, and am going to ask @smurthas or @temas (or anyone else) to take this since they know that subsystem ;)