<bugfix>Allow only a single MissingPackage exception to be included in an InvalidPipeline container exception</bugfix>
<bugfix>Allow only a single MissingPackage exception to be included in an InvalidPipeline container exception</bugfix>

core/modules/module_registry.py:
  - MissingPackage._module_id: new property, override field with property that always returns None
  - MissingPackageVersion._module_id: new property, override field with property that always returns None

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