Prefix log filename unhelpful

[whyrusleeping]

There are lots of logs using prefixlog that print out a message, but give no indication of where that message originated from, since the log function is being called from inside prefixlog. This can be solved by increasing the value of ExtraCallDepth on the logger object itself: https://github.com/op/go-logging/blob/4d186fb040e7e748df3736262acc9816156cc194/logger.go#L88

[jbenet]

@whyrusleeping yeah I opened op/go-logging#44 before the ExtraCallDepth merged to master. We just haven't updated to the new version and changed logger to deal with this.

[jbenet]

This requires:

• vendoring op/go-logging again instead of my fork
• wrapping go-logging to fit our StandardLogger interface (i.e. what my fork did)
• setting the ExtraCallDepth in the prefix logger.
• moving everything to use one logger (i think we want eventlog)

Nice:

• moving the logging stuff out of util and into its own package (util/logging ?)

Long term good idea (though this still needs work):

• move everything to use logrus -- https://github.com/sirupsen/logrus

I started on this here: https://github.com/jbenet/go-ipfs/tree/fix/logging/stash -- but i'm shifting to do something else, sorry. that branch is basically a stash.

[jbenet]

Closed in #1359