[build] don't compile natnet if not needed
[modules][messages] mission: LLA waypoints in 1e7deg instead of float

A 32bit float has 23bits for the mantissa, which is a bit more than 7 digits.
Since you already use 3 digits to represent the part to the left of the decimal point, that leaves about 4 digits for the rest..
So in the worst case of 180deg you have a resolution of only ~3m!

With 1e7deg 32bit int you get ~1cm resolution.

addresses first part of #984 (at least for the rotorcraft version, fixedwing version still converts to LLA float in between...)
[modules] mission_rotorcraft: only check for ned_initialized_i
Merge pull request #986 from paparazzi/mission_module_latlon_int

[modules][messages] mission: LLA waypoints in 1e7deg instead of float

A 32bit float has 23bits for the mantissa, which is a bit more than 7 digits.
Since you already use 3 digits to represent the part to the left of the decimal point, that leaves about 4 digits for the rest..
So in the worst case of 180deg you have a resolution of only ~3m!

With 1e7deg 32bit int you get ~1cm resolution.

In the fixedwing version LLA is still converted to float first, since we seem to miss functions to convert LLA to UTM in int or double...
At least it is better for rotorcraft and same as before for fixedwings...
[messages] remove description node again for now

seems server/GCS (OCaml lib) can't handle it, as they fail with
Fatal error: exception ExtXml.Error("Error: Attribute 'type' expected in <<>>")