check we can run expts in the loss domain

[drbenvincent]

In an experiment I am writing with discounting in the gain and loss domain, there are problems with constructing a set of designs with DesignSpaceBuilder in the loss domain. Need to pin down where this problem is and fix it.

Delayed choice

• [ ] ensure we can do time discounting experiments in the loss domain
• [ ] add an alternate constructor
• [ ] add some tests

Risky choice

• [ ] ensure we can do risky choice experiments in the loss domain
• [ ] add an alternate constructor
• [ ] add some tests