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.
Merge branch 'master' of github.com:StackStorm/stanley into pack_virtualenv_sandboxing_and_isolation
Move run_command function in a separate util module.
Move function for determening sandboxed process PYTHONPATH into sandboxing
util module.
Add tests for sandboxing utils.
Remove unused imports.
Inherit pythonpath from the parent process.
TriggerPublisher -> TriggerCUDPublisher.

We will now have two trigger publishers - existing one which publishes Trigger
model CUD events and a new one which publishes Trigger events inside sensor
wrapper.
Merge branch 'pack_virtualenv_sandboxing_and_isolation' into sensors_process_sandboxing
Also blacklist "packs" pack name for user packs.
Use system python binary for running python actions which are part of the system
packs.