xconsol.py: will automatically pick up data column if corrected column is not available; chaaverge=False for mstransform; xplotcal will skip plotting if the table is not predefined.
update docs about the weighting adjustment;  drop examples; xconsol.py: unflagging a vis record if some channels are still good (like MIRIAD/INVERT slop=1); WEIGHT is redefined as the channel weight rather than the spw weight based on the bandwidth; xutils: new functions checkchflag/unchflag