Make Pylint more flexible with a YAML-based config

See also: pytools#4 (closed)

This adds support for a YAML-based config file format for Pylint with a thin wrapper script that translates the YAML file into command line arguments.

This change also modifies prepare-and-run-pylint.sh to look for YAML configs. It looks for a .pylintrc.yml, and if it does not find it, it downloads the global config file from ci-support. It also supports local configurations via the file .pylintrc-local.yml.