Summary of changes:

- Revamped the config/state system (CodaLabManager replaces config_parser).
- The BundleCLI and BundleRPCServer take the manager.
- Removed env_model; contents moved to state.json now.
- New entry point: cl.py, which includes both server and client.
- New syntax to switch client::worksheet: 'cl work dev::nlp'
- Support for aliases of addresses (including 'local').
- Ditched old config files; new ones are not compatible.
- Integrated prompting for password if trying to connect to remote server.
ensure using Python 2.7 with virtualenv
update cl.bat to use cl.py for Windows
slim down cl worker output so that printing only happens if interesting things are happening
Merge Percy's changes