TMF: Add abstract XY line chart viewer on top of SWT chart

TMF: Add abstract XY line chart viewer on top of SWT chart

* Provides a viewer for line charts. With this viewer, all series will use
the same X axis data.
* It automatically creates series as values are provided for a key.
* A tooltip shows the values for each series at the selected x position.
* Series can also be manually added and the returned series can be modified,
so while "line chart" is the default representation, it can be used in other
ways.

Change-Id: I90b63e1dc87a1dbd49d37ff99fb22e04eecad2be
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/20342
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
IP-Clean: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>