Documentation for application.properties overrides via ENV variables

[hweej]

User to override application.properties via environment variables. ENV variables are currently supported in a limited or full-supported way, however it may not be clear to the end user.

Use case:

It would be helpful for users to be able to

1. Point to specific VEP version of genome-nexus. e.g. <vep_version>.genomenexus.org
2. Modify the enrichment fields via environment variable

Alternative (instead of ENV variables)

1. User supplied application.properties file. Not friendly for usage in NextFlow

Deliverables:

1. Provide examples of ENV usage, especially with docker usage.
2. Provide example of user supplying custom application.properties file and location to file.
3. Document the ENV variables currently being used