Making Queries Configurable

[Pothulapati]

Right Now, The queries are present in the queries.go file and are specific to linkerd.

To make this repo support more implementations, we need a way to make the prom quieries pluggable. This can be solved by having each implementation have a ConfigMap with the queries.

The corresponding ConfigMap is installed and dynamically loaded as a configuration field into Viper during initialisation.

@grampelberg

[Pothulapati]

I will be working on this issue, once this approach is accepted :)