Another baby step towards #123, this change follows from #192 and merges
the two concepts of Origin in a renderable node. We also cut out a layer
of abstraction, and add an OriginTable method to Report, which directly
generates a table of info for the detail pane given any origin node ID.
Other changes from feedback:
- Assume origin IDs are unique and don't reflect.Dedupe
- Improve origin ID lookup
- Move OriginTable to detailed_node.go, as a free function
- rm app/detail_pane.go (empty)
- All HostMetadata information becomes NodeMetadata
- Significant change to mechanics, but same net effect
- LocalNets becomes "local_networks", space-separated list of CIDRs
- Load becomes simple single string
- Use MakeHostNodeID for indexing into Host topology
- (That changes the app /origin/{id} handler; will be removed later)
