Select the test set to run

The widget launcher script has been modified to use the environment
variable VERBSELECTED and VERBARGS. Then you are able to select a test set
defined by the testVerb configuration section in your JSON configuration file.

You can also use the special argument {'lavaOutput': true} to enable specials
Lava markers on the output.

Change-Id: If677cbbc8cb6cf6eb1bdf9f76b83f5e7976dd5a5
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>