using .env file messed with the env variables in the CI, reverting to old way of doing things in a more readable fashion

removed EXPOSE cmd in frontend's Dockerfile.dev and added empty dependencies to CI stages that don't need artifacts for efficiency

WS-195, WS-76: Notification System now working and sending emails on request submission and completion

- made our volume mounts dynamic with ENV variable
- changed our test deployment trigger with git tags as end-of-sprint-[0-9]+

- simplified branch and image tagging in CI
- minor cleanup of CI scripts

This reverts commit 68320db2.

- Added PATH_PREFIX variable to build stage to handle dockerfiles at paths other than /services
- removed .unit-test template from .gitlab-ci.yml because it was duplicated