Named return variables should only be used to describe the returned type
further, e.g. `err error` doesn't add any new information and is just
stutter.
This puts all collector-specific flags into their own namespace under
"collector.<collector-name>", and moves from camel case to dashes, which
is the standard in Prometheus land now.
This allows static metrics (e.g. an attributes collector replacement),
and cronjobs to expose stats by echoing into a file.
For example:
echo "my_metric 123" > mycronjob.prom.$$
mv mycronjob.prom.$$ mycronjob.prom
