Suppress unneeded/duplicate columns in requirements
Some more tests for jobtypes api
More consistent data spec for requirements

When specifying new software requirements in a put to a jobtype, the
required software and its min and max versions are specified as strings,
while a POST to the requirements collection for a jobtype would expect
those as ids.

This commit changes the latter endpoint to expect the required software
and its versions as strings as well.
Corrected return code
Suppress unneeded or duplicate columns in output
Docstring/logstring fixes
More fixes for jobtypes API