[pgAdmin][RM5048] : code coverage tool

Hi Team,
Please find the attached patch to calculate code coverage if pgadmin
code(python tests).
I have extended the existing testsuite to enable coverage. I have used
python's coverage module.

*Some useful commands: *

before running the commands make sure you create .coveragerc file under
/regression directory(details mentioned in README)
Run coverage

With all modules
run 'python runtests.py --coverage --exclude feature_tests'
With specific module
run 'python runtests.py --pkg
browser.server_groups.servers.tests --coverage'

Thanks!
--
*Regards,*
*Navnath Gadakh*