Graphite deals poorly with metric names containing quotes.

Sanitize graphite metrics with our own escaping function,
better suited for this use-case than the one in `utils_parse_option`
Merge pull request #525 from collectd/feature-better-graphite-escape

Graphite deals poorly with metric names containing quotes.
redis allows passwords up to 512 characters long
Merge git://github.com/octo/collectd