Allow control over log level on server

[jkomoros]

Currently if you're not in release mode it goes to debug level.

But there are even cases in dev mode where you don't want verbose

[jkomoros]

Also, it really should be that each manager just gets a reference to the single logger that server has, so when server emits other debug messages like socket registering they use logrus too

That implies that manager.Logger is a public field, and server creatse a new logger and stuffs it in at start

[jkomoros]

Just use logrus.StandardLogger(), and pass that to gin as well

[jkomoros]

• [x] In server replace all calls to log to s.logger.Log
• [ ] GIN should use standardlogger (https://github.com/gin-gonic/contrib/blob/master/ginrus/ginrus.go)
• [x] renderer.error should log error
• [ ] in server package a lot of calls to errorln in the last few commits use logrus wrong; should use WithFields (that is, the varidaic arguments include a Fields object but should use WithFields then call to ErrorLn).
• [ ] in server package a lot of calls to logorus would do better to have more info in Fields
• [ ] Have a standard entry to WithFields on top of in server to include things like gamename, gameid, user
• [ ] Have a command line flag for verbose or something