swtbot: check syntax highlighting with filter bar

swtbot: check syntax highlighting with filter bar

This test will take a screen grab of the cell being highlighted
and compare it before and after highlighting.

Change-Id: Iae5fe05cc965b19aa5dec775c26e1b637901982b
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/44540
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>