Added ability to duplicate a workflow or send it to another user

[Anthogr]

• 2 new buttons added to duplicate/send a workflow
• When clicking on one of those buttons for a specific workflow, all the entries in the database and all the generated files relative to this workflow are duplicated
• Clicking on send button will lead to a new page where the receiver of the workflow can be chosen
• New column state added in data_files table of the database in order to track if the workflow has been duplicated/sent