<bugfix>MissingPackageVersion exceptions need to be tied to specific modules</bugfix>
<bugfix>MissingPackageVersion exceptions need to be tied to specific modules</bugfix>

Revert earlier change that assumed that MissingPackageVersion exceptions could be collapsed when they exist for more than one module.  The upgrade logic uses these exceptions on a per-module basis.

core/modules/module_registry.py:
  - MissingPackageVersion._module_id: **removed** property

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