Remove extra spaces from Debug output, insert delimiters between fields

Summary:
When a single query is streamed, the fields may be separated with multiple
spaces, while subqueries, which are streamed via recursion from QVector,
may lack any spaces between fields.

Disable any automatic insertion of spaces and add delimiters manually
where necessary.

Reviewers: Baloo, Frameworks, ngraham, poboiko, astippich

Reviewed By: astippich

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D17160