Neuron name service: add basic settings infrastructure
Neuron name service: add basic name generation and client update

This commit extends the neuron name service to generate names for each
skeleton it manages. Currently, this is only the base name fallback and
no data is requested from the back-end, yet.
Neuron name service: add skeleton ID as display option
Neuron name service: add support for all and own annotation labeling
Selection table: let 'sort by name' use neuron name service
Neuron name service: support meta annotation based labeling
Graph widget: retrieve names from name service
Compartment graph plot: use name service for labeling
Connectivity widget: get neuron labels from name service
Connectivity widget: remember checkbox states on threshold change
Neuron name service: support neuron renaming

This adds a convenience method to the neuron name service which to rename a
neuron. If the renamed neuron is managed by the name service (i.e. if there are
clients displaying this neuron), all clients are notified about this change.
Neuron name service: reverse display of fallback list

It is more natural to see labeling that applies first on top of the
list. Therefore, the current display is reversed: one adds always to
the top of the list. This, however, is only true for the display and not
for the actual name service.
Neuron name service: add option to append skeleton ID to labels