Allow namespace argument in metric package

[mantzas]

Is your feature request related to a problem? Please describe

The metric package use patron as namespace by default.

Describe the solution

Add a namespace argument to all function in the metrics package.

[mantzas]

metric.go contains a setup function that can be used to setup globally the namespace.
The setup function has been used in service construction, but all the code that comes before is initialized with the old value which is "patron".
This metric setup should have before everything else. Ideal place is patron.SetupLogging(name, version) which is run before all. Ideally the name of the function should change to simple Setup. Cli should be changed accordingly.