A module should be able to use the return keyword

Refs #35
phantom.injectJs should be able to load internal scripts

When the main script is an internal script, given script name
to injectJS should be resolved against the internal URL of the
main script. It should not be searched on the file system.

Refs #35
Fixes configuration reading for script handlers

Default values of parameters should be set on the slConfiguration
when there are not indicated on the command line.

Fixed also default value of native parameters.
Re-enable ghostdriver and fixes configuration issue

Refs #35