Add logging levels TRACE and NOTICE (or allow adding custom log levels)

[gamato]

picologging looks very interesting but one thing we do miss is a few extra logging levels.

Could you please add logging levels TRACE and NOTICE ?

They both are used in other popular logging frameworks, in Python and elsewhere.

It would help us a lot as custom log levels are not supported in picologging.

The log levels would be ordered as follows:

CRITICAL ERROR WARNING NOTICE INFO DEBUG TRACE

Thanks in advance!