fw landing: use terrain estimate from global pos
Merge remote-tracking branch 'upstream/terrainaltfield' into fwlandingterrain
Merge branch 'hildistancesensor' into fwlandingterrain
Merge remote-tracking branch 'upstream/terrainaltfield' into fwlandingterrain
fw landing: if using terrain estimate, don't switch back during landing
Merge branch 'terrainaltfield' into fwlandingterrain
remove warnx
Merge remote-tracking branch 'upstream/fwlandingterrain' into fwlandingterrain
fw landing: impose horizontal limit for start of flare
Merge remote-tracking branch 'upstream/master' into fwlandingterrain

Conflicts:
	src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
Merge branch 'flarehorizontallimit' into fwlandingterrain

Conflicts:
	src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
Merge remote-tracking branch 'upstream/master' into fwlandingterrain
fw landing: horiz flare check: fix wp distance

better calculation of wp distance when behind wp
make flare pitch angle a param
Fixed delay calculation of laser
flare pitch limit: apply at throttle lim altitude
Merge remote-tracking branch 'upstream/master' into fwlandingterrain
inform in GCS when switching to laser
fw pos control: add param to enable/disable usage of terrain estimate during landing
Merge pull request #1341 from PX4/fwlandingterrain

FW landing: use terrain estimate