Port SNOW-322 to SG2.0: Improve double-click handling of the MiniMap

Relevant SVN commit from Snowglobe 1.x (https://svn.secondlife.com/linden/projects/2009/snowglobe/trunk)t:

• r3093 : SNOW-322: Improve double-click handling of the minimap. Set tracking target to click position or teleport directly. Depends on setting introduced in SNOW-352 / SNOW-668. Patch by Be Holder and Ardy Lay.

Test Plan: note to tester: this feature works hand in hand with the "Double-click Teleport" feature introduced in Sprint 3

• Launch viewer and log in
• Bring on the Develop>UI and click on Double-Click Teleport
• Bring on the minimap
• Click on a location on the minimap
  -> Verify that you teleport there and the minimap stays up
• Zoom out the minimap and double click on a nearby region
  -> Verify that you teleport there and the minimap stays up
• Bring on the Develop>UI and click on Double-Click Autopilot
• Bring on the minimap
• Right click on the minimap and click "Stop Tracking" if it's on
• Double click on the minimap on a spot which is several meters from your avatar
  -> Verify that the world map opens and that a tracking beacon is set where you clicked, verify that the coordinates displayed on the world map and location spinners show the beacon location
• Dismiss the world map
• Double click the minimap again without turning "Stop Tracking"
  -> Verify that the world map opens but that the previous tracking beacon hasn't been lost