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.
If I do that then I don't get the behaviour that I want. How I want it to work, and how it works right now, is:
1. If a user is not logged in, and they attempt to access a view which requires a staff user, they get asked to sign in.
2. If a user is logged in as a non-staff user, and they attempt to access a view which requires a staff user, they get the 403 error page.
3. If a user is logged in as a staff user, and they attempt to access a view which requires a staff user, they get the page they requested.

If I make the change you suggest then in situation #1 above the user gets the 403 page, as opposed to being redirected to the login page. Perhaps that is fine, as an admin user would probably know that they need to log in, but I do prefer the current flow.

I did have to experiment with this quite a bit to get it working the way I have it, but maybe there's a better way to do it than what I have now. I would rather keep it as is and keep the existing behaviour than change it as per your suggestion and lose that behaviour, but I am open to convincing.