Draft: Copy required Gemnasium files

Summary

This merge request makes the following changes:

• Copies over the cli, finder and scanner logic
• Renames all gemnasium instances to dependency-scanning
• Removes all builder logic
  • There's no logic for parsing Go as this will require gitlab-org/gitlab#229819
  • There's no logic for parsing Gradle as this will require gitlab-org/gitlab#229817
  • There's no logic for parsing Maven as this will require gitlab-org/gitlab#478562
• Removes dependency-scanning report logic
• Removes all vrange references

Links/References

Related to gitlab-org/gitlab#476165 (closed)