ADS-B aircraft visual altitude info request

#### Issue details
https://discuss.ardupilot.org/t/uavioni-ping-ads-b-receiver-data-on-flight-screen/36957

Without mousing over every aircraft, there is no way to know the altitude and collision potential or risk. TCAS and other manned aviation systems always have number floating with every object, and that number has a 2-digit +/- value in hundreds of feet that reports position. Displaying the altitude would be the second most-important piece of information after position. Since position is adequately handled, altitude should be displayed next.

#### Version
All

#### Platform
[ ] All
[ ] AntennaTracker
[X] Copter
[X] Plane
[ ] Rover
[ ] Sub

Start with the linked discussion and the existing ADS-B aircraft display in Mission Planner. Done means altitude information is visible for each displayed aircraft without mousing over it, for the Copter and Plane platforms.

Written by the indexing model from the issue text.