added option [-maxmesh #] to auto assign nfm

added option [-maxmesh #] to auto assign nfm per cm, so that the fm size
is less than #. The normal place to assign nfm per cm is now a
multiplier to allow for areas of higher density meshing
added venus test case for maxmesh option
Merge branch 'maxmesh'
merged maxmesh, added examples: venus and pfbr