Added MCNP interface for source sampling.
Changed tag names and mode indexing (MCNP idum numbers are indexed from 1).
Doc strings.
SG fixes
Made Fortran API non-specific for MCNP.
Starting documentation.
Adding doc file.
All code in documentation works.
Final Cleanup.
Removing source.F90
Added new source.F90
Merge pull request #512 from elliottbiondo/fortran

Fortran interface to Sampler class