Bug 1005404 - Add ability to create task within tool

This is my first attempt to implement the features requested by bug 1005404. This includes:
- Changes to the model to support the new metadata for tasks
- A form that an admin can use to create a new task
- A form that an admin can use to edit an existing task
- A listing that an admin can see with all tasks, from whence they can choose one to edit and also can click a button to be taken to the "new task" form

Everything seems to be functional and working, and matches the spec in the bug, including limiting access to admins. The form *does not* look good. It needs css work, and that is far from my forte. I am hoping that someone currently on the project can help with that, or perhaps we can recruit someone to help with it.

As for the django code, I am definitely uncertain about a lot of it, so I am hoping for feedback from @Osmose. As I said, I believe that it all works, but I'm not sure if I did a lot of it correctly, including how I dealt with assets and the .less file.
It does work, and it's not really bad in and of itself, but future changes to the form will become a pain if you continue to customize your form input by editing the widget. In the long run it's just way easier to write your own HTML than rely on HTML generated by the widget in cases like this (normally it's fine to just use the widget-generated code because it's just a single `<input>` tag) because then you don't have to track multiple places to figure out how the input is being rendered.

This isn't a blocker though. Just keep in mind in the future when this form gets any more complex you'll want to abandon widgets and write form HTML yourself.