haptic expanding sphere

Description

• additions to haptic guidance to choose shrinking sphere or expanding sphere
• examples for expanding sphere
• LinearTrajectory divide by zero bug fixes

What to focus on

• put content here.

Reviewers

• @cw
• @amyblank
• @bz
• @ps
• @alexluleme

Resources

Issues

What issues does this fix?

• Fixes #issue-number