avocado.utils: Add tools for Avocado development [v2]

There are few things I'm using and someone else might be interested too. I added avocado.utils.debug for these functions. Also I added couple of docs about Eclipse and other python profiling tools. I'm not sure, where to put these and if they are really required, so feel free to yell at me :smile:

v1: https://github.com/avocado-framework/avocado/pull/298

Changelog:

    v1: Use `avocado.debug` logger instead of `print`
    v1: Slightly modified output (PERF keyword for easy grepping and units)
    v1: Added **kwargs