Added support for Azure Data Explorer datasource plugin

[Git-Lior]

What does this do?

Add support for Azure Data Explorer queries in grafanalib

Why is it a good idea?

Azure Data Explorer is offered as a plugin datasource in Grafana and adding this will let people create graphs based on data from Azure Data Explorer.

Context

Azure Data Explorer is a log analytics cloud platform optimized for ad-hoc big data queries.

[hanagiat]

This is a great addition, waiting for approval and merge to use it