TMF: Consolidate some view code into the AbstractTimeGraphView

TMF: Consolidate some view code into the AbstractTimeGraphView

This new view is a base view for all views using the TimeGraphCombo widget.
As a first step, the lttng2 kernel Control flow view and Resources view have
been modified to extend this abstract view.

Mostly all of the interface management code (build thread, zoom thread, signal
handling, etc) is in the base class.  Final views need only implement to code
to fill the entries' list and events.

This patch includes:
- The abstract view class that all new time graph views may extend.  The default
  weight of each sash can be set in the child view.
- A TimeGraphEntry class that can be used as is if the view does not require
  extra data of its entries
- Modification of the TimeEvent class to add a value to it.
- Added a ITimeGraphDrawingHelper interface to pass to the presentation
  providers to help them get the information they need to know where to draw
  some things (see ResourcesPresentationProvider)

It is a first step before adding new features to the time graph views.  Some
more abstraction may need to be done as well as other reorganizing of the
code.

Also updated for the 2.1 API, added a ITimeGraphPresentationProvider2 interface
to avoid API breakage.

Change-Id: I73c9f1b4bf8ec265f1b02804fa7f819bd2b8dd7a
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/12423
Tested-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
IP-Clean: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
IP-Clean: Alexandre Montplaisir <alexmonthy@voxpopuli.im>