* Fix ioss memory leak in creating superelement

* (LOW) Create an element set containing the elements for each part.  Would
   need to fix Ioss to handle element sets.

* (CHECK) Fix problem with sideset element mapping -- I think element blocks
   are in a different order, so the element mapping is incorrect.

* (MEDIUM) Fix so node and element global id maps are preserved as much as possible.

* (?) Add subsetting (exclude specific grouping entities)


DONE:
* nodeset ids are not propagated to output database...
* need progress meter on output

* Timestep subsetting

* Option to create a nodeset containing the nodes for each part.
   Could move all of the parts nodal variables to nodeset variables on
   this part.

* implement variable subsetting (all, none, variable list).

* Handle duplicate grouping entity ids.  
  -- This is working for non-merging of grouping entities.
     - Each entities name is prefixed with p#_ where # is the part number 1..num_parts.
     - Duplicate ids are renumbered.

* Handle salinas use case.

* Handle merging of nodes and/or elements based on global id or
   geometric proximity
   -- I think global id matching of nodes OK
   -- Matching by proximity should be working now also at least for 2 parts;
      - Multiple (more than 2) part matching needs testing.


GJOIN DIFFERENCES:
- Does not combine blocks/sets that have the same id/type.
