v0.2.0: Implement free text query (#2)

* Add free-test queries to the manual test script

* Add free-test queries to the daatsource script.

* Fix comments.

* Update README.

* Fix exmaple weathermap config.
Add a warning about overloading prometheus with expensive free-text queries.

* Fix typos in comments.
Revert changes to the range-ventor in the interface queries; unintentionally committed from lab testing.

* Fix order of in & out metrics in example free-text query.