Add methods on Repository to manage hook
In hooks, move data stuff from view to models.EventManager

We will soon fetch events from github and we'll this too
Add a check_events in hooks, to act like hooks but by fetching the events API
Correct the FetchIssueByNumber to have many tasks for the same repo
Minimize a race-condition when posting/editing

Steps:
1/ the comment is posted by the user
2/ a task is created
3/ the task starts running
3.1/ the comment if fetched via its ID
3.2/ the comment is pushed to github
3.3/ the comment is updated locally
3.4/ a task to fetch the issue is created
4/ the task ends

Before this commit, if a(nother) fetch of the issue is done between 3.1
and 3.4 (maybe via a hook just received), 3.4 fail because "self.object"
refers to a comment that does not exist anymore.
Why ?
Because while fetching the issue, the comment just created, not in the
just fetched data, is deleted. And in 3.3, a *new* comment is created,
with a new ID.
In can happen easily if two people are discussing an issue at the same
time.

By reloa the last "self.object" by "comment", to access its issue, it
works because the comment does not need to be fetched from the DB again
and we don't care of it, we just want the issue.

Note that other race conditions can happen, for example if the parallel
fetch occurs during steps 1 or 2, all created or edited comments for the
fetched issues will be vanished.

A solution could be to only delete *already fetched* objects when
deleting during a fetch.
Remove bad property (with argument !!??)
Add a "clone" method to our Job model

Fields to copy must be specified in the `clonable_fields` attribute of
the Job.
The new job can be delayed by passing `delayed_for` or `delayed_until`
to the  `clone` method. If none, the new Job will be queued to be run
ASAP.
The property of the new job will be `0`, but it can be passed to the
`clone` method too.
Remove print when checking repo events
Add tasks to regularly check hooks and events
Better managing of github connections in hooks tasks
Correct fetch API endpoints when repo without issues
Stop the worker when a DatabaseError is raised

sqlite: "database is locked"
postgres: "current transaction is aborted, commands ignored until end of transaction bloc"
Add 0 to 10 seconds to the fetch events task requeuing
Allow passing raw form data to github