Add pack management action for setting up virtual environment for the provided
packs.
Update "packs.uninstall" to also remove pack-specific virtual environment (if exists).
Remove test code.
Use a constant instead.
Use action-specific logger instead.
Default "config" attribute to None.
Rename file, add metadata file and run the action as part of the install action.
Use values from the config.
Use consistent directory structure - store all the JSON metadata files in a
top level actions directory.
WIP: Change packs base dir to /opt/stackstorm/packs/
Make "get_global_config_path" method public.
Make get_and_parse_config method public and a classmethod.
Use safe_load instead of load.
Stub out a wrapper class for running sensors classes sandboxed in separate
process.
Stub out new container class which runs each sensor in a separate process.
Merge branch 'master' of github.com:StackStorm/stanley into pack_virtualenv_sandboxing_and_isolation
Move run_command function in a separate util module.
Use a better key / variable name - filename -> file_path.

Also update affected tests.
Merge branch 'master' into sensors_process_sandboxing
Make get_trigger_types method a class method.