Add functionality to display edges in neuron populations with missing nodes

[napakalas]

Problems:

• Not all neuron connectivity nodes in SCKAN are available in FC/AC.
• Some neuron connectivity nodes are centerline, e.g. UBERON:0001759, and mapmaker cannot determine the node's associated sub-segment.

To display continuous connectivity, missing nodes and nodes with undetermined centerline sub-segments are skipped by connecting the available nodes.

Next, an interface is required to enable/disable the edges passing through the missing nodes and display the missing node information on the card.