Takeoff Mission Item Issues

#### Issue details
The takeoff mission item does not contain a header where the normal pitch angle column should be. This is an issue since the last beta update that I did today.


When adding takeoff and land WP's, the takeoff pitch angle and altitude cannot be changed. I always use 30-degrees as my takeoff angle and make the altitude the same as the survey waypoints. These "parameters" of the mission item should be an option in the menu that can be saved - just like all of the survey parameters that save for each mission. I've had numerous crashes and close-calls because the takeoff line was left at the default settings and not re-checked. This would prevent that.

Finally, there should be a pop-up box that warns users before writing a takeoff mission item with anything less than 10 degrees to a plane. To get around the issue above with the wrong parameters in the takeoff mission line, sometimes I add the takeoff line manually. Changing a mission line to takeoff changes its altitude but NOT its angle. That causes users to miss the 0-degree takeoff angle that causes crashes immediately.

#### Version
1.3.61 build 1.3.6910.18181

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

Reproduce the takeoff and land waypoint behavior in Mission Planner version 1.3.61, focusing on the mission-item editor and the takeoff pitch and altitude fields. Done means those parameters can be edited and saved like survey parameters, and a warning appears before writing a plane takeoff item below 10 degrees.

Written by the indexing model from the issue text.