Add status to tasks

[RignonNoel]

For the moment we can only set a task to True or False, it could be nice to have a status management.

MODEL

• Create a new model Status (project_id and name)
• Delete field open on Task model
• Add a new foreign key status to the new model Status

API

• Add call to add a new status on a project
• Add a call to list status of a given project
• Add a call to remove status
• Add a call to edit status
• Refactor Task calls to manage status and stop use open field