Move pangolin-data out of docker image

[talnor]

What needs to be done: Although the setup with downloading pangolin data into the docker container works, it is a sensitive setup. It would be good to be able to define a specific version of both gms-artic and the docker containers to work with to have a robust setup, while still using the latest pangolin data.

Suggestions on how to get it done: For nextclade we have the command nextclade dataset get to download the most recent nextclade data. Something similar would be good.

For pangolin, two options are:

• The following command will update versions of pangolin, pangolin-data, scorpio and constellations to the latest tagged releases:

  pangolin --update-data

• It is also possible to specify a data directory when running pangolin to use instead of the installed data:

    --datadir DATADIR
                          Data directory minimally containing the pangoLEARN model, header files, 
                          UShER tree and alias file. Default: Installed pangolin-data package.

Info available on usage and installation.

What are the arguments for getting it done:

Task is considered finished when: pangolin updates does not rely on docker image updates