Move examples/simple-open-loop-policy to sandbox
Add license header to core/**/*.txt

- to hello-world.txt
- to external-ip-address-resolvers.txt (which also required code to
  treat # at the start of a line as a comment)
software-base: add license headers to files

- though these files are boring, might as well include the header
  rather than having to justify why we missed them out.
example-simple-messaging-pubsub: include license header

- though the file is boring, might as well include the header
  rather than having to justify why we missed it out.
Explain rat exclusions for licence headers

- and add license header to a few more files
Exclude sandbox/** from RAT checks

- sandbox is not included in distro; don’t fail main build because
  a file in sandbox is not compliant.
Fix simple-open-loop-policy compile errors
Fix SoftwareProcessSshDriverIntegrationTest failure
This closes #230