Use 3rd party icons in CRW plugin registry instead of invisible ones

Some time ago, we switched all the plugins' icons to a generic empty 1px icon so that they'd disappear.

We discussed this change with UX and it was decided that rather than seeing 100s of the same icon (Che or CRW) it was more meaningful to hav NO icons.

But for Che 7.21.2, it seems the 264 plugins' icons are now meaningful and generally unique, with only 5 bearing the Che logo:

While for CRW 2.5, most of the icons have been removed for the 54 plugins, except where we a PR snuck an old icon in:

So I suppose the question here is:

• is it time to re-add the plugin icons from upstream to downstream, and if so,
• is there any code in the upstream plugin registry that hasn't been downstreamed into the CRW plugin registry fork that would be needed for this?