cmake needs update to make it more robust

[qingfengxia]

1. to help cmake to find MOAB installation folder
   export LD_LIBRARY_PATH=/opt/moab/lib is not a cmake way to help detect MOAB
   export MOAB_ROOT=/opt/moab/
   cmake .. -DCMAKE_INSTALL_PREFIX=..

2. some other missing dep is not documented, such as gmp, mpfr, but it be installed toghether with some other lib.

3. On some linux, LD_LIBRARY_PATH does not help to find library on standard location, such as export LIBRARY_PATH=$LIBRARY_PATH:/home/qxia/Repositories/dagmc_bld/MOAB/lib does not help on link time, but
   export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/qxia/Repositories/dagmc_bld/MOAB/lib help in link time

I had fix, shall I send PR

[makeclean]

the new standards for cmake tell you it should be -DMOAB_dir I think