Add support for Loggly-style ingestion tokens

[markdascher]

Papertrail recently added support for syslog ingestion tokens using Loggly's [TOKEN@41058] STRUCTURED-DATA format, as an alternative to assigning unique ports to each customer. This PR allows remote_syslog2 to send using that format.

/etc/log_files.yml would look something like:

files:
  - /path/to/your/file.log
destination:
  host: logs.collector.solarwinds.com
  port: 6514
  protocol: tls
  token: 012345-ABCDEFGHIJ_klmnopqrst

Already tested it out and confirmed that logs showed up in Papertrail, using a token from Settings > Log Destinations > Token.

[luk3thomas]

LGTM