Add environment variable to enable recursive mode

What does this MR do?

Expose an environment variable named RECURSIVE. This variable controls LicenseFinder's --recursive CLI flag. See https://github.com/pivotal/LicenseFinder/blob/master/README.md#output-from-project_roots

Using the --recursive option means the array will include subdirectories that contain a known package manager. With the exception that Gradle and Maven subprojects will not be included.

Prior to this change RECURSIVE is hardcoded and cannot be set by users.

What are the relevant issue numbers?

NONE

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • CI Templates (to be removed)
  • Vendored CI Templates (also in CE)
  • Ensure that all of the ENV vars supported are propagated to Docker containers upon docker run in job definitions
• Conforms to the code review guidelines
• Security reports checked/validated by reviewer