Generate task json route

[KellyRousselHoomano]

Add a route to generate a json configuration file of a task from description of requirements

Edit task creation route to insert new md_text_type on the go if output_type provided in json task does not exist yet for convenience Update related documentation:

• swagger
• sales assistant example
• create new task

I also added "datetime" field in task_spec.json and update associated documentation for convenience