Use a Config struct to set LogLevel

[hgzimmerman]

The WebLogger currently defaults to a Trace log level. I would like to avoid having Yew-framework-specific information printed to the console by specifying an Info log level. I think the typical way this is accomplished is by passing a Config struct to the init() function that allows specification of log level, as well as other features like formatting of the log messages.

I'll see if I can get something working in a day or two.