dashboard: UI feedback

[aaronkaplan]

Feedback from the Graz workshop:

The dashboard should look like this:

• overview page -> top half is the map
• bottom half is a "filesystem tree view" of nodes. Filter button gets removed. If you click on a node, then it expands and shows all the devices.
• if you want to edit a node/device/interface/etc click on edit
• enable expansion and closing of a sub-tree
• "Owner"/"Eigner" column should read "role" ("Rolle"): "manager", "owner", etc.
• make a green/red/yellow dot which indicates reachability. Static link to an image on a stats server...
• if you click on the red/green/yellow dot, then you get the statistics image. If you click on anything else in the device, you get the details of the device.

[tanzer]

Except for the reachability/statistics dots, this is implemented by https://github.com/FunkFeuer/common-node-db/commit/3e013c816bb3b21abd1ac23d979c33cb7582d69f, https://github.com/FunkFeuer/common-node-db/commit/c02de135e48a70f1ef6319ba27ae1133adadc661, https://github.com/FunkFeuer/common-node-db/commit/58a21150e472a5f4095dbd2f5de4eefad8a25126, and https://github.com/FunkFeuer/common-node-db/commit/fd3812c68efe51722e04a8d73ec107c5dcc615e4.

For the reachability/statistics dots, we need a API how to get that information: same problem as for https://github.com/FunkFeuer/Graz/issues/31.