Neuron dendrogram: allow multiple comma separated tags to be highlighted

What is missing, though, is the correct display of the tag names next to
the node. Currently, the complete tag list is displayed instead of only
the matching tag.
Neuron dendrogram: increase vertical space for leaf nodes
Connectivity widget: add selection synchronization and select-all

The selection state of a skeleton in either upstream, downstream or input table
is now synchronized. Additionally, a select-all checkbox is added for the input
table, which is kept updated as well when the selection changes.

Closes acardona/CATMAID#841
Closes acardona/CATMAID#728