Better logging options

[mitchellh]

Originally reported by @blalor

We need to provide better options for logging that isn't geared towards humans. I think this should probably entail both syslog and a file option.

[blalor]

Ideally there'd be an option for outputting structured messages via JSON, including timestamp, level, component, etc.

[mitchellh]

We use a pretty machine-friendly format. The truth is, internally we only get them as a string as well (with a timestamp), no component, nothing. Just a string.

We leave the parsing of the logs up to logstash or some higher level citizen.

[carlivar]

I think this should probably entail both syslog and a file option.

This is technically only half completed, since it requests both syslog and file. I'll file another issue about file logging though.