Add a slider on the main viewer screen to adjust draw distance

(Test plan is still UNDER DEVELOPMENT, as we're in the process of defining the expected behavior for this feature.) 1. Hover over binocular icon near top right corner of the SL window. Verify that the slider pops up 2. Click and drag the slider knob up and down (don't release the mouse button for now) Verify that the numeric draw distance indication changes accordingly Verify that the draw distance is applied immediately (objects appear or disappear) 3. Release the slider knob at a setting below 280 m (No warning message should pop up) 4. Use the slider to set your draw distance to above 280m and release the mouse button Verify that now, a warning about possible performance decrease pops up. 5. Click OK. (Without checking 'Don't show me this again.') 6. Repeat steps 1-4, verifying the same behavior as before. 7. Check 'Don't show me this again.' and click OK 8. Repeat steps 1-4, verifying the message does not appear at all, now. 9. In the Preferences floater, tab 'Notifications', select 'Warn me if I adjust draw distance to a large value' in the 'Never show' field and move it to 'Always show' using the up-arrow button. Click OK to accept the change and close the Preferences floater. 10. Repeat steps 1-4 and verify the original behavior occurs again (i.e., warning message only at step 4) 11. Click OK 12. Hover over binocular icon again (slider pops up) 13. Click the gear icon at the lower end of the slider Verify that Preferences floater opens with the Graphics tab active. 14. If the draw distance setting is not visible in the Preferences window, click the button 'Advanced'. (Otherwise, no action needed.) 15. Hover over binocular icon again (slider pops up) and move the slider knob Verify that the setting change is immediately indicated accordingly in the Preferences floater (numerical value and slider knob position)