MetView should work out of the box

Currently, in order to include the MetView dependency on Dataflow, we require users to build their own custom container image and pass specific dataflow arguments in the `weather-mv` command. In the ideal case, users shouldn't have to worry about docker containers or passing the right arguments; regridding should work out of the box.

## Implementation notes
- Short term approach: Publish a public docker image that has MetView installed on a Dataflow worker image.
- Medium / long term approach: Publish a public docker image that has miniconda installed. Allow us to modify our `setup.py` build command script to run `conda install` commands during the setup.