Update the last two btest FAF tests.

  - Small changes were done to the ftp log.
Undoing the FTP tests I updated earlier.

 - Fixed the external tests btest config too.
Fix various documentation, mostly related to file analysis.

- Fix examples/references in the file analysis how-to/usage doc.

- Add Broxygen-generated docs for file analyzer plugins.

- Break FTP::Info type declaration out in to its own file to get
  rid of some circular dependencies (between s/b/p/ftp/main and
  s/b/p/ftp/utils).
Add a distinct tag class for file analyzers.

This should prevent assignment mismatches between file and protocol
analyzer tags.
Factor out the need for a tag field in Files::AnalyzerArgs record.

This cleans up internals of how analyzer instances get identified by the
tag plus any args given to it and doesn't change script code a user
would write.