Allow the customization of the measurement names

[JonasKunz]

At the moment, measurement names are derived based on the OpenCensus measure which corresponds to the view exposing the data.

E.g. if a view with the name http/responsetime/sum corresponding to the measure http/responsetime is exported, the resulting influxDB measurement will be http_responsetime with the field sum.

In inspectIT Ocelot we implemented a way of exposing percentiles without the standard OpenCensus views. For this reason, we need a way of customizing the measurement name resolution.