Describe the problem

Currently, the docker recipe assumes the image should be built from the OpenEMR repo.

Describe the solution you'd like

Converting the git url to an argument in docker recipe can allow the builder to specify a fork's url instead. This can be helpful when building an image for a clinic while awaiting for patchsets to be ready for official release. It also allows for building base images using experimental changes for which you would like to simulate the typical build and release workflow.