v1.2.2

Updates from May-December 2020
-- added correlated-in-time gains to synthetic data
-- added (back) simultaneous Stokes I and polarimetric imaging
-- standardized synthetic data options for movie and image
-- fixed several bugs in multifrequency imaging
-- fixed bugs in dynamical closures
-- fixed bugs in load_uvfits for VLA data sets
-- fixed bugs in saving uvfits