This PR takes the existing Linear Descent option for RTH and enhances it. Firstly, Linear Descent is now no longer an RTH type. If previously using `AT_LEAST_LINEAR_DESCENT`, you should now just use `AT_LEAST` as the RTH type. Linear Descent is now a separate option that can be used with and other RTH type. To do this, the target altitude of the descent is now the `nav_rth_home_altitude`. In some cases, if flying below the home position, this could even be a linear ascent.
An option has also been added to decide how far away the linear descent starts. This is via the `nav_rth_linear_descent_start_distance` parameter. Current behaviour can be maintained by setting this to `0` [default]. You can also specify a distance from home when the descent begins. This is in metres and be up to 10km away. Of course, this value can be adjusted if required.
- No flickering of display confirmed
- Correct update rate confirmed
- Fixed issue with `msp_displayport_fullframe_interval`, forgot it had switched from uint to int.
All good to go
Changed redraw method to call `MSP_DP_CLEAR_SCREEN` before sending only dirty characters. This will have the same effect as sending everything. But will have less data to send.
Re-worded the docs, to make them easier to understand.
I found that setting this to 0 causes the update of the OSD to virtually stop. I guess it is simply too much data to be sent every 62.5Hz. Even set to 1, the OSD is responsive.
This PR increases the maximum safe distance for the first waypoint to 1500m. A lot of fixed wing LR pilots are frustrated with the 650m limit. This corrects that while not increasing the memory used by the variable. I didn't see any reason for this to be in cm. It's not divided anywhere. So metres is much more fitting.
The current min and max for `tz_offset` is 1440, or 24 hours. The actual min and max for UTC is -12 hours (-720) and +14 hours (840). This PR uses the UTC values as the actual min and max offsets.
