Use message bus & library module

[La0]

This big PR moves most of the pulselistener logic into a submodule pulselistener.lib. The intent is to create in a near-future an indenpendant library with that source code. Each project now has a dedicated event listener (note the name change...). Each library module is independant. They can be chained through a MessageBus implementation using async & multiprocessing queues.

modules

• bus has the MessageBus implementation, used to communicate across projects. Each part self registers its required queues
• mercurial has the Repository tooling (no more Mercurial worker)
• phabricator has API access to phabricator instance, helpers, and publication loop
• pulse has listening capabilities on any remote queue
• taskcluster simply has hook trigger capability
• web has the webserver in dedicated process for receiving HTTP notifications
• monitoring has the code-coverage dependant logic for mail reports (might be removed or moved to code-coverage repo as it's really specific)

code-coverage

• Listen for pulse messages,
• Filter those pulse messages and check if they match code coverage criterias
• Filtered messages trigger a new TC task creation
• New TC tasks are monitored, a report is regularly sent through email

code-review

• Runs a webserver in a separate process (Heroku requirements)
• Clones configured repos
• Phabricator build are received on the webserver route,
• Each build is "enriched" with stack patches + related commit messages (when the build is public)
• Enriched build is then applied on the local clone
• When successful, it's pushed on try
• Publication on phabricator is dependant on outcome of previous steps (working, error, treeherder link)