Adapt to changes in core-api e14b395

VisualAttributes now have positional meaning. VisualAttributes enum in
core-api introduces static forSequence(), which should be used instead
of AbstractI2b2Metadata::convertVisualAttributesString().
Fix error handling in QueriesResourceService

When there was a problem running the query in QueriesResourceService,
the method was supposed to recover and write information about the error
on the database.

Unfortunately, postgres was aborting the transaction at this point, so
the data saved before the error would be lost and the error logging
information would not get written. This commit fixes this problem with a
SAVEPOINT, which allows the transaction to be recovered.

Also improved some (log4j) logging statements.
Fix error in last commit

By combining the savepoint statement with the insert, .executeUpdate()
stopped reporting the number of rows inserted. Fix by separating them
into two statements.
Merge remote-tracking branch 'transmart/master'