allow components to set rpm_package_name

setting rpm_package_name in a component config yaml file will allow
a user to override what the name of the rpm should be.

When rpm_package_name is unset anvil defaults to the existing
functionality, which is using the name of the component, or, if it is
a python component we are packaging, the output of the component's
"setup.py --name" command
Merge pull request #381 from jaybuff/rpm_package_name

allow components to set rpm_package_name