A more General DD Gain Specification

[SpheMakh]

Describe the problem that the feature should address
Arrays with multiple antenna types are not supported. Support arrays with multiple antenna types, and other DD Gains (DDGs)

Describe the solution you'd like
Allow:

1. Multiple primary beams. Or, just DDGs
2. DDGs to be specified for sets of antennas, e.g

DDG:
  DD1: # apply to all antennas
    file: DDGfile01.fits 
  DD2:
    file: DDGfile02.fits # apply to a subset
    antennas: [1,5,6, 10~15]
  DD3: # apply to a subset
    file: DDGfile03.fits
   antennas: [16~24]