Revamped configuration system / generalize cl run

    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.

    Change the nature of RunBundles to make them more general and more like
    MakeBundles in that we have an arbitrary collection of targets, not just a
    program_target and a input_target.
    Now you can type:
      cl run date
      cl program:svmlight input:wine 'program/run input output'
      cl :svmlight :wine 'svmlight/run wine output'