Umbraco logger should be wrapper

[bielu]

Similarly to https://github.com/serilog/serilog-expressions umbraco logger should be wrapper around loggers, so we can actually write to different sink and stop using file based sink. :)
Edit:
got feedback that is not clear, so let me describe it little more.

Currently umbraco has hardcoded implementation in Umbraco serilog sink which use File based logging, my proposition is allowing move it to any type of sink which user want to use instead of using hardcoded file one.