delete mavlink header files
mavlink as git submodule

Mavlink is now a git submodule because auto generated header files are
available at https://github.com/mavlink/c_library
Better logging
More logging
change mavlink submodule url
add mavlink submodule check script

The script checks if the mavlink submodule is up to date
really remove mavlink folder
Added NuttX submodule
Add proper NuttX submodule checks
Cleaning up sub modules
Fixed .gitmodules
Added NuttX
Fixed check tools
Turn instructions into a makefile command, allowing Windows GUI kids to create a make target in Eclipse just for this
Merged master
Turn off noisier logging
Merge pull request #1137 from DonLakeFlyer/FTPLogging

Better FTP logging
bugfixes for checks and tools
Merge pull request #1143 from PX4/submodules

Submodules for MAVLink and NuttX
Merged master into offboard2_merge