Merge pull request #12 from PX4/master

update beta from master branch
adjusted exposure time to max 64 lines, reduced flow calculation to be performed at 5x5 different positions within 64x64 pixel image, minimized horizontal blanking time to achieve 400Hz update rate
Merge branch 'master' into beta
Merge pull request #16 from PX4/beta

Beta
fixed quality measurement with new number of blocks
Merge branch 'master' of https://github.com/PX4/Flow
fixed dependency on Firmware repo in makefile
updated upload script, fixes bad character error message
-added micro second counter to increase precision
-enabled low light mode without HDR but increased desired brightness
-extended I2C frame with accumulated flow/gyro values between readouts
readout check of new I2C frame prohibits compatibility with old version, implemented 2 checks, compatible with old I2C readout know
I2C frame1 and frame2 are now totally independent, both protected during readout
added serial output throttle factor, adjusted i2c integral frame to output millirad*10, cleaned up main loop and I2C tx update function
Update MAVLink, use default dialect
Change to default / common dialect
Fix API and repeated declarations of UART interfaces, fix meaningless parameter index comparison
Updated MAVLink version
Removed unused dialect
added optical_flow_rad mavlink message, added gyro_temperature to I2C and mavlink interface
fixed gyro scaling issue, added temperature readout (not tested)
added proper M_PI in degree to rad conversion, added gyro temperature offset and converted to temperature*100 centi-degrees celsius resolution