Abstract out assignments into tasks

[cormander]

As a campaign manager, I need to create tasks for volunteers so that we can provide clear instruction as to what needs to be done within the tool.

This feature is done when:

• A new task creation API exists
• Tasks require a form, a list ("turf" or otherwise), and a text description
• A task status API exists
• The "/hello" endpoint is updated to pull assignments from tasks if they exist

[cormander]

In neo4j context, the schema ought to look something like:

(:Volunteer)-[:ASSIGNED]->(:Task)
(:Task)-[:TASK_FORM]->(:Form)
(:Task)-[:TASK_TURF]->(:Turf)
(:Task)-[:TASK_LIST]->(:List)
(:Person)-[:RESIDENCE]->(:Address)-[:WITHIN]->(:Turf)
(:Person)-[:LIST_PERSON]->(:List)