<bugfix>Fix parameter explorations on File parameters</bugfix> <ticket>#412</ticket>
<bugfix>Fix parameter explorations on File parameters</bugfix>
<ticket>#412</ticket>

Instead of casting a parameter value using str(), we need to use the
constant's translate_to_string method as types that are objects like
File will not convert correctly using str().

gui/paramexplore/pe_table.py:
  - QParameterExplorationTable.collectParameterActions: use registry
    to obtain constant module and call translate_to_string static
    method to obtain string value for ModuleParam

hjanime/VisTrails,celiafish/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,minesense/VisTrails,minesense/VisTrails,celiafish/VisTrails,minesense/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,Nikea/VisTrails,celiafish/VisTrails,Nikea/VisTrails,minesense/VisTrails,Nikea/VisTrails,minesense/VisTrails,hjanime/VisTrails,hjanime/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,Nikea/VisTrails