Add labels as env-variables when calling monaco

[grabnerandi]

Right now when Monaco CLI is called by the monaco-service it only passes KEPTN_PROJECT, KEPTN_STAGE and KEPTN_SERVICE as env variables. We should extend this with labels so that every label will also be passed, e.g: KEPTN_ENV_LABEL1=label1value ...

This opens up some interesting new use cases where labels can be used when deploying new dynatrace configuration, e.g: you can reference a label value in a created dashboard ...