UI: Timeline with nested calls

Patch for issue #52:
vogleditor: timeline does not display apicalls which are nested in the
            tree control
Cause
-----
* vogleditor_QTimelineView::paint()

   The search for the apicall at which to draw the timeline marker
   was only looking at the top-level apicalls. If the apicall was
   nested then it wasn't checked.

* vogleditor_QTimelineView::drawTimelineView()

   If the top-level apicall's duration didn't meet the threshold for
   drawing its location on the timeline then its children were also
   skipped.

Patch
-----
* vogleditor_QTimelineView::paint()

   Add recursive checking for nested apicall items

* vogleditor_QTimelineView::drawTimelineView()

   Regardless whether the parent duration met the threshold, continue
   looking at the children. If the threshold is met for the child then
   the child's location is drawn on the timeline.

Testing
-------
A version of glxgears that has 3 levels of nested apicalls using
glPushDebugGroup/glPopDebugGroup and glBegin/glEnd (bin file attached)

Signed-off-by: Lawrence L Love <lawrencex.l.love@intel.com>
Merge pull request #97 from lawlove/nest-timeline-patch

UI: Timeline with nested calls