#72 SimpleTimelineDisplay as AbstractCallableTool

[Craig Nicol]

The following changes are required to turn the sample SimpleTimelineDisplay into a proper AbstractCallableTool

* Move into package hierarchy beside other tools.
* Populate NiteTimeline via corpus getElements or similar to allow display of all elements in corpus by default.
* Make default layer name include colour and agent to minimise overlaps within layers.
* Make default depth use recursive depth in layer to minimise overlaps.
* Find reasonable default label (probably nite:id or getText or empty string)
* Read corpus settings:
* * delegate or attribute for layer, label and depth
* * multiple annotator / resource loading