include gmsh-to-xdmf conversion in io.py module
new function common.io.convert_msh_to_xdmf
for conversion of MSH to XDMF from within Python (in addition to the cli script)
Edited by D.J. Nolte
new function common.io.convert_msh_to_xdmf
for conversion of MSH to XDMF from within Python (in addition to the cli script)