Restore ability to pass in pygeoapi configuration file via docker volumes syntax

Related to and prerequisite for #5 (closed)

Background

The base pygeoapi docker image supports the ability to override the default configuration using a -v (--volume) switch. This allows the user to provide a custom config.yml file with the need to clone the repo and build their own image locally. With how the current image generation is structured in this repository that feature is no longer supported and there is not a mechanism to update the config file without rebuilding the image. This behavior is undesirable because any team member that wishes to update and test a new config for a pygeoapi tool, must also be trained in on how to build and run docker images from this repo.

Closure Criteria

• Docker files and tooling have been modified to support override of config via -v.
• Entrypoint.sh has been updated to apply tooling to convert our custom config file into the standard pygeoapi format