This class shall be used to map external metrics from Prometheus, InfluxDB, ...
to well-formed Monasca metrics.
It supports:
* filtering by name (regex)
* renaming of metrics
* renamign of dimensions
* filtering by dimension value
* transforming of dimension values (regex based)
Change-Id: If0a5fdb1126bdfc93a88d5c1c7266d0c152d925f
