Fix possible errors in the DPDD level 1 tables

In going through at least the level 1 catalogs, I think there might be some errors or inconsistencies in the tables in the DPDD that are causing some confusion and can be clarified.

• In DIAObject table, the description for fpFluxMeanErr is "Standard error of fpFlux" whereas psFluxMeanErr is "Standard error of psFluxMean". Is it standard error of *Flux or *FluxMean?
• In SSObject table, for oeCov should the covariance matrix length 28 and not 21?
• In DIASource table, should parentSourceId really be parentDiaSourceId and the description should refer to deblending from another diaSource, not Source?
• In DIASource table, should the dipCov covariance matrix length be 21 instead of 15?