[RFC] Remove the 'Configuration Nodes' sidebar

With 1.1.0 introducing the outliner in the Info sidebar, it occurred to me that the Config Nodes sidebar is much less useful.

The Outliner:

• includes a 'Global Config node' section
• lists config nodes that are scoped to individual tabs
• can be searched and filtered

What it doesn't (currently) have (compared to the Config Node sidebar) is:

• an indication on how many nodes use the config node
• an easy way to list out the unused nodes

The first can be easily solved by added the count to the node label - just need to make sure the right editor events are fired whenever that user list may change.

The second could be a filter option - is:unused or similar. The deploy prompt saying you have unused config nodes could provide a click-through action to pre-fill that filter in the filter box to show them.

This is just an idea at this point. If we think there is a compelling reason to keep the config node sidebar, then it needs a general overhaul anyway.

I'm raising this issue because I'd like to keep some quick feedback on the idea. If it can be done for 1.1.0 so much the better. Otherwise it can be put on the slate for 1.2.0.