SVM: Make the X/Y naming convention consistent between catalogs

[stscijgbot-hstdp]

Issue HLA-525 was created on JIRA by Michele De La Pena:

The Point and Segment catalogs use different terminology for the "X" and Y" catalog column names.  Make these names consistent in all output catalogs, including "reg" files.  Also, remember to update any other modules (i.e., svm_quality_analysis) to look for these new column names.