tmf: Support horizontal scroll with mouse wheel in time graph

tmf: Support horizontal scroll with mouse wheel in time graph

Horizontal scroll can now be performed using Shift+MouseWheel while over
the time graph control state area.

MouseWheel over the time scale, marker axis and horizontal scroll bar
will now perform horizontal scroll, while Ctrl+MouseWheel over those
same controls will now perform horizontal zoom.

Table of MouseWheel actions:

modifier:      None       Shift      Ctrl     Shift+Ctrl
time scale     hScroll    hScroll    hZoom    hZoom
time graph     vScroll    hScroll    hZoom    vZoom
marker axis    hScroll    hScroll    hZoom    hZoom
h.scrollbar    hScroll    hScroll    hZoom    hZoom
v.scrollbar    vScroll    vScroll    vScroll  vScroll
outside (Win)  vScroll    vScroll    vScroll  vScroll

Change-Id: I0e48dd37b121b934ef872509aa721506876ca199
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/68464
Reviewed-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>