temp commit:
snIa.py runs, but I cannot get the x0 values to work. This is because I am getting strange behaviour when I get columns using column_by_name(). This seems
to return a null array while I expect it to return an array of size self.nobjs

Example:
   @compound('snra', 'sndec', 'z', 'vra', 'vdec', 'vr')
    def get_angularCoordinates(self) :
        _snra, _sndec, _z =  self.column_by_name('raJ2000'), \
                             self.column_by_name('decJ2000'),\
                             self.column_by_name('redshift')
        #_snra = self.column_by_name('raJ2000')
        #_sndec = self.column_by_name('decJ2000')
        #_z = self.column_by_name('redshift')

        #Why does len(_snra) give zero? should it not be of size self.nobj
        #Yet the addition with np.zeros(self.numobjs) seems to work correctly
        print 'snra', len(_snra)
        _sndec += np.zeros(self.numobjs)
        _snra +=  np.zeros(self.numobjs)
        _vra = np.zeros(self.numobjs)
        _vdec = np.zeros(self.numobjs)
        _vr = np.zeros(self.numobjs)
        return ([_snra, _sndec, _z, _vra, _vdec, _vr])
has output :
python snIa.py
Duplicate object type id -1 specified:
Output object ids may not be unique.
This may not be a problem if you do notwant globally unique id values
/astro/users/rbiswas/soft/sims_catUtils/python/lsst/sims/catUtils/baseCatalogModels/__init__.pyc
/astro/users/rbiswas/soft/anaconda/lib/python2.7/site-packages/sqlalchemy/dialects/mssql/base.py:1124: SAWarning: Did not recognize type 'geography' of column 'geopoint'
  return fn(*arg, **kw)
snra 0
snra 0
snra 32956