Contrib/limit leecher events

[tweak-wtf]

This PR limits the aquarium.leech events dispatched by the leecher.

List of supported Aquarium Events:

• item.created.Asset
• item.updated.Asset
• item.created.Shot
• item.updated.Shot
• item.created.Sequence
• item.updated.Sequence
• item.created.Episode
• item.updated.Episode
• item.created.Task
• item.updated.Task
• item.updated.Project
• user.assigned
• user.unassigned

[ymoriaud]

@tweak-wtf Can I merge the pull request or you still want to work on it ?

[tweak-wtf]

from my side this is ready. thanks for checking it out :)