Update seldon metrics

[ukclivecox]

• Updates the dashboard
• Creates a doc for analytics describing prometheus metrics and the grafana dashboard
• Ensures the correct labels are added to deployments.
• Removes the whole deployment JSON for being sent to the engines as this causes canary deployments to force an update to all predictors running which is not correct for isolation of predictors - changing one predictor should not effect any others.
• Adds a python module for REST and gRPC requests used by all example notebooks