Pull request #902: CAS-14195
Merge in CASA/casa6 from CAS-14195 to master
* commit 'd74c9a0ba4ec491506f98bf594b2710a3258278a':
For CAS-14195, tidy up doc info in fringefit.xml
For CAS-14195, improve inline documentation for corrcomb parameter.
changed np.alltrue to np.all for new test case
For CAS-14195, added combine='spw',concatspws=True tests to Fringefit_corrcomb2 test
For CAS-14195, add new Fringefit_corrcomb2 test class to test new corrcomb modes (requires new dataset in the DR)
For CAS-14195, ensure corrcomb='stokes' and 'parallel' duplicate the combined-poln solution is duplicated to both polarizations within the output caltable (as was done for corrcomb='all' previously).
For CAS-14195, in fringefit task and underlying mechanics, add support for correlation combinations: 'stokes' (which does formal Stokes I combination of parallel hands, strictly respecting flags; formerly 'all') and 'parallel' (which does optimally weighted parallel-hand correlation combination for all available unflagged data)