Update pangolin: Add database usage options

[pvanheus]

FOR CONTRIBUTOR:

• - I have read the CONTRIBUTING.md document and this tool is appropriate for the tools-iuc repo.
• - License permits unrestricted use (educational + commercial)
• - This PR adds a new tool or tool collection
• - This PR updates an existing tool or tool collection
• - This PR does something else (explain below)

[pvanheus]

As discussed on Galaxy Public Health Gitter, the pangolin tool should specify options for using a specific pangoLEARN DB. Either

1. Download the latest version and use that
2. Use a version built in to the Galaxy server (from a data table)
3. Use the "default" version installed with pangolin (not recommended)

The choice between 1 and 2 will depend on the configuration of the Galaxy server, its internet connectivity, etc.

This is WIP as the builtin DB option is waiting for #3617 to get merged.

[bgruening]

@pvanheus you need to add the boilerplate loc files and the
tool_data_table_conf.xml.sample files.

Ideally, you could add a test as well for the loc file option. See for example this one as an example: https://github.com/galaxyproject/tools-iuc/tree/master/tools/artic

[pvanheus]

@pvanheus you need to add the boilerplate loc files and the
tool_data_table_conf.xml.sample files.

Ideally, you could add a test as well for the loc file option. See for example this one as an example: https://github.com/galaxyproject/tools-iuc/tree/master/tools/artic

Yes, that is what is in the latest set of commits. I have now removed the WIP as I think this is ready for review.