Create abstract log pane (trace pane)

[bestchai]

After a model is inferred, create a new pane that is a more abstracted version of the log. This could be something like one box for each trace, which would show only some identifier (unique ID, the execution separator group like IP, etc.) and would be expandable to show only that one trace.

This new pane could mostly replace the log after initial input. For example, clicking on an edge could highlight the boxes for any affected traces, and expanding any such trace's box would show the specific event that is highlighted. It would be easier for a user to view individual executions, select executions to view together or remove, etc.

[Issue created by ohmann: 2015-11-24]