Use logging from gbp and delete the msger module

Use logging from gbp and delete the msger module

As gbs already depends on gbp it makes sense to use its logging facility
instead of msger, which is copy&pasted from another project. Gbp logging
is based on standard Python logging functionality. It basically only
adds color output to it. This change adds a minimal functionality to the
'gitbuildsys.log' module to act as a GBS-specific logger.

This change is also takes more than 400 lines of code from the project
and decreases amount of pylint errors on more than 30% (120->84)

Change-Id: I4bd4d2b9299bf7aa79d5ea9da182312d53e8c3ff
Signed-off-by: Ed Bartosh <eduard.bartosh@intel.com>
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>