Pull request #863: CAS-9957
Merge in CASA/casa6 from CAS-9957 to master
* commit '60c4540243eb8ce72f8f074d4fd56ccb910b3563':
refactoring
refactoring using slice functions
npol=4 is not supported
put const before type
Refactoring for consistent coding style
define weightMat as reference
renamed weightspec to weightSpec CAS-9957 handle the case when both Wxx and Wyy is zero
Use built-in types instead of casacore type, also use consistent types in for-loop CAS-9957 updated formula for WEIGHT column case CAS-9957 implemented correct weight propagation
