run-tests.sh: Add support for coverage report

This requires the coverage python module. You enable it by calling
run-tests.sh with the --coverage (-c) flag.
run-tests.sh: add --verbose flag
Add test target to Makefile
Add a pylint target to top level Makefile
Merge pull request #33 from olof/topic/runtests_improvements

Improvements to the run-tests.sh script