More FTP support

Added:
- sequence numbers
- directory list returns file sizes
- open command returns file size in data
Updated mavlink version
Merge pull request #1265 from PX4/FTP

More FTP support
Ensure that a failing dataman start does not abort boot
If we failed loading params, reset them (if the file handle is valid the file is corrupted and there is no hope, if its just not present the reset command will not do anything)
Increase timeout in an attempt to prevent timout python failure
Fixed feedforward naming
Merge branch 'master' of github.com:PX4/Firmware into fw_att