Generate coverage xml

for cobertura style coverage information that can be picked up
by e.g. Jenkins
Fix typos

Git-Dch: Ignore
Add .coveragerc

To get correct report if coverage is invoked directly (not through
nose/disttools) in order to get an xml report, for example.

Currently only used for restricting the coverage output to the gbp
python package. That is, same thing that 'cover-package' option in
setup.cfg does.

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
GitRepository.show: use _git_inout()

Instead of the deprecated _git_getoutput() method. Also, capture stderr
and put the error message to the exception, instead.

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>