BibFormat: fix CLI call to old PHP-based formatter

* Escapes output format in shell when calling old PHP-based BibFormat.

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
Merge branch 'maint-0.99' into maint-1.0

* maint-0.99:
  BibFormat: fix CLI call to old PHP-based formatter

Conflicts:
	modules/bibformat/lib/bibformat_engine.py