Teach logStash to optionally log to a local file

* File logging is in addition to Redis/UDP logging
Teach logStash to accept static key/values from the config file

* Example:
"logstash": {
    "static_keys": {
        "hostname": "host.domain.com",
    }
}
Merge branch 'logstash_file' into logstash
Merge branch 'logstash_static' into logstash
Remove "@" from field names

* See https://tobrunet.ch/2013/09/logstash-1-2-0-upgrade-notes-included/
Change logstash access logging to be less restrictive on output fields
Change file logger to support arbitary values in log formats
Bump version number
Merge branch 'logstash'