Frame of Reference revised to be thinner and with sharp vs. rounded corners.

The revised / corrected Frame of Reference will appear:

• Immediately in new Map Builder exercises.
• Upon opening existing Map Builder exercises that are owned by you
• When the owner of a Map Builder exercise shared with you as Read-Only opens the exercise

Map Builder: Bug fix: Zoom slider now works properly on touch devices

Bug fixes and backend upgrades:

• several bug fixes completed (front-end and back-end)