navigator: skip takeoff if already above takeoff altitude
mission: takeoff and next waypoint related fixes
Upgraded unit test framework
FTP: Add new open command for write.

All open commands now return file size.
FTP: Implement write command.
FTP: Add truncate command.

Unfortunately NuttX not provides truncate(),
had to be emulated by copying with O_TRUNC flag.
FTP: fix truncate errors. Also correct errno reporting.

Seems that warnx() everytime changes originak errno to EINVAL.
FTP: Rename command.

Payload: `<oldpath>\0<newpath>`
See: man 2 rename
FTP: Add file checksum calculation command.
navigator/mission.cpp: indentation fixed
Merge branch 'master' into takeoff_fix
navigator: autocontinue fix
Merge remote-tracking branch 'upstream/master' into takeoff_fix

Conflicts:
	src/modules/navigator/mission.cpp
FTP: Save errno in _copy_file().
FTP: Return bytes written in payload.
Fixed function name of mission modification logic, attributed @DrTon
Merge pull request #1279 from PX4/takeoff_fix

navigator: skip takeoff if already above takeoff altitude
Merge pull request #1360 from DonLakeFlyer/UnitTestFramework

Upgraded unit test framework
Merge pull request #1363 from vooon/ftp_write_support

FTP: write support
Compile fixes in navigator