Use print as a function

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Improve output of ReBench

- refactor code to do all the reporting related operations in the reporters
- move all commonly relevant output to CLI reporter using print() instead of the loggers
- reduced output that is shown unconditionally
- leave very verbose things to be activated with -d option

- fixes issue #10

Signed-off-by: Stefan Marr <git@stefan-marr.de>