Make sure there are no uppercase letters in domain names (Fixes #25)
Make sure there are no uppercase letters in domain names (Fixes #25)

- safe_string - generates a domain safe string
- Apply this to REPO_NAME_SAFE and BRANCH_NAME_SAFE variables
- Also make sure DOCKSAL_DOMAIN is lowercase

docksal/bitbucket-pipelines-agent,docksal/bitbucket-pipelines-agent