CRF: allow schema names to be used for Viterbi tables

JIRA: MADLIB-765
Fix crf_test_fgen, vcrf_label, and vcrf_top1_table (was: vcrf_top1_view)
 to allow schema names in table name parameters. Output of vcrf_label is
 now a table instead of a view (see comments in vcrf_top1_table).