See the itaps/imesh/iMesh_extensions.h function for details of these functions and how to use them.

Three new iMesh extension functions are added: iMesh_createTagWithOptions, iMesh_stepIter, and iMesh_tagIterate.
The first two were needed before the tagIterate function could be used.  Unit test and example codes are also added
to test this.

Besides changes for the above, this commit also has the following changes:

iMesh_f.h: change iMesh_EntityIterator to iBase_EntityIterator, same for array-based version.
iMesh-Defs.inc.in: add @PNETCDF_LIBS@ to IMESH_LIBS
itaps/imesh/Makefile.am: added more -I locations, and new MOAB_iMesh_extensions_tests test program
tools/vtkMOABReader/Makefile.am: added another library to LDADD
configure.ac: replaced check for vtkRenderer.h with one for vtkRenderingInstantiator.h, that seems to be a 
  better header to look for; also added another default location to check for vtk; also added examples/itaps
  to the list of makefiles to create
examples/SetsNTags.cpp: changed to namespace'd MOAB calls

Passes make check in serial and parallel.



git-svn-id: https://svn.mcs.anl.gov/repos/ITAPS/MOAB/trunk@5082 6162379e-bd28-0410-9a7d-b7f4dcfcad3c