roles: Add collector_scripts

This role is meant to deploy various prometheus collector scripts which should output textfiles in prometheus format to be scraped by e.g. node_exporter.

It can easily be expanded upon by writing a {{ collectorscript }}.j2 and placing it into the correct template directory. After that the {{ collectorscript }} needs to be added to the list of enabled collectors via ansible vars (see defaults/main.yml). The needed systemd services and timers are created accordingly and automagically.