Add analysis for gradle projects

What does this MR do?

This MR gives gemnasium-maven the capability to analyze gradle projects. The gemnasium-maven analyzer is updated to detect build.gradle and initiate a gradle analysis phase by using the gemnasium-gradle-plugin to process the dependencies in the project and output an artifact list which can be scanned by gemnasium.

Checklist:

• include running gemnasium-gradle-plugin
• add path to analyze gradle
• update gemnasium to allow scanner/parser to detect this new dependency type
• update Dockerfile with dependencies for both types of analysis
• ensure output from gradle analysis makes sense
• switch to a tagged version of Gemnasium, after merging gemnasium!53 (merged) and go mod tidy

Testing:

• create a test project following the project template
• verify supported versions of gradle

What are the relevant issue numbers?

gitlab-org/gitlab#13075 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE; TODO: add link to MR, in gitlab project
• [-] 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
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer