DOC: dev guide: explain /opt/dev_intelmq
DOC: dev guide: explain /opt/dev_intelmq

and /opt/intelmq
fixes certtools/intelmq#1300

certtools/intelmq,certtools/intelmq,aaronkaplan/intelmq,aaronkaplan/intelmq,aaronkaplan/intelmq,certtools/intelmq