Merged with master
Merged ETS airspeed driver
Merge branch 'gps_vel' of github.com:PX4/Firmware
Improved GPS update rate calculation
Implemented new led status proposal
New blink patterns for safety switch, removed GPS lock indicator
Use work_queue instead of thread
fix capitalisation of include file name

Marko Pagott <p0rc0.jet@gmail.com>
Hotfix: Wrong capitalization on header file name
Hotfix: Wrong capitalization on header file name
Merge branch 'master' of github.com:PX4/Firmware
Merge branch 'master' into gpio_led
Merge branch 'master' into new_led_status
Change the way modules are built so that object paths are relative and use vpath for locating sources (so source paths are also shorter).

Add some basic documentation for the build system files while we're at it.
Oops, left in some test code.
Tested with PX4FMU and PX4IO with GPS and arming
Fix ROMFS dependency scan, add a warning if ROMFS_ROOT appears to be empty.
Fixed led patterns to be up to the latest specs
Added fixed wing controller example
HOTFIX: simplify symbol names going into the ROMFS object, hopefully this avoids inconsistent symbol naming on Windows.