webglapp: better handling of mouse event functions and their removal.
webglapp: don't show the active node if not visible.
Would get shown when updating its position.

While at it, fix the logic in the overlay: only invoke the method when
a treenode is activated.
object tree: properly expand to selected skeleton upon initialization
and remove some friction by caching a reference to some DOM elements.
Merge branch 'master' of github.com:acardona/CATMAID
Removed synchronization for Treenode and Connector Table widgets.

Was adding friction to tracing for very little gain. The 'Refresh' buttons
are there for this purpose. Plus, refreshing a table with several thousand
treenodes every time a new node was added or removed was never a good idea.