Automatically generated altitudes for intermediate WPs

It would be helpful if MP could generate altitudes for intermediate WP's to keep a constant gradient. For example, say I want to maintain a constant gradient climb between two waypoints, but I then want to add some WPs along the way to alter the lateral path. By right clicking on the altitude field and selecting auto-generate, the altitude required to maintain a constant gradient defined by the last and next WP will be filled in.
This would be useful when wanting to maintain a constant gradient in the turn at the end of a flight line. These turns are often defined by 4 WP's, and adjusting all their altitudes can be a chore.
This can also be useful when creating an approach path for an auto landing. Autolandings are most successful when a constant descent gradient is used. With this feature, you could set the initial WP altitude and let MP figure the altitudes for the rest of the WPs that define the traffic pattern.

Start by locating the waypoint altitude field and its right-click context menu in Mission Planner. Trace how the last and next waypoints define altitude and position, then determine how the auto-generated values should preserve a constant gradient for intermediate waypoints. Done means the requested menu action fills intermediate waypoint altitudes for flight-line turns and approach paths.

Written by the indexing model from the issue text.