Improved the data load process

Problem: when the file name is different from the data set that it
contains, the file will be reloaded even if SMART=t is used.

Solution: In "tables.yaml" files, the user can add a new "contains" field
which is a comma separated string containing all the data set names in
this sql.gz file. If the madlibtestdata schema already has all of these
data sets, then this file will not be reloaded.

pros: Save data loading time

cons: need to edit the "tables.yaml" files to add this "contains" field
for data files that are not consistent with the data sets. This is
mainly for LDA data sets, which has been taken care of in this commit.