alternative behaviour for metaAsColumns=false

[GeekyDeaks]

When using the option metaAsColumns=false everything is considered meta, even the log level and message, so you only ever end up with a meta field in the table. I felt this was unexpected based on my experience with other transports, but I appreciate that it may well be as designed, hence the wording of the commit message.

This change omits the level and message elements from the meta when metaAsColumns=false

It's probably still not ideal. The core transports appear to only use the message element when outputting and rely upon the format chain to create the appropriate message, but doing that would not make use of the azure table features. Maybe there should be an option of which fields to pull out of the meta?

Any thoughts?

[GeekyDeaks]

ah - this is not as simple as I initially thought. format.splat() creates a meta element, which I think it would be better to use, as it closely emulates the way v2.0 of winston worked.

I'll submit an update, but this one is going to be a more sweeping change as it will also alter the way metaAsColumns=true works

[GeekyDeaks]

Ok, I have dug into this way further than I ever intended :)

There appears to be an issue with winston.js polluting the format object if the first parameter is an object, which I suspect is causing the pollution I am seeing when using metaAsColumns=true.

I have raised it in the main winston.js project: winstonjs/winston#1510

If it really is an issue with winston.js and not by design, then it reduces this change to nothing more than a workaround