ros_sql: optional echo SQL to console
Revert "allow strings with null characters to be saved to postgres"

This reverts commit c919a77fb42e97322ed76ea56caa8779fbbe7bca.

This breaks automatic decoding of said fields to python
strings (i.e in resultswebbrowser)
print errors using rospy logerr and show the offending topic
add more (currently failing) tests
bugfix: nested types and prefixes work together now
Merge remote-tracking branch 'origin/strawlab-electric' into work-on-sqlite

Conflicts:
	nodes/ros_sql
	src/ros_sql/factories.py