AP_GPS: Improved accuracy of NMEA driver

The conversion of ret (32bit-integer) to float reduced accuracy to ~9cm or ~22cm. Now it's ~1cm.
Rover: try changing GPS setting to AIRBORNE_4G

this may reduce the GPS latency and improve chicane performance
HAL_PX4: fixed build for new PX4Firmware
Copter: disable OPTFLOW for PX4/Pixhawk
Copter: disable OPTFLOW for SITL
Copter: remove PID logging

Almost never used and eats up limited log description space
Copter: add time to ATT, MAG, CURR dataflash msgs
Copter: add TimeMS, InavAlt to CTUN df msg
Copter: combine NTUN and INAV dataflash msgs
AP_Notify: external LEDs blink while initialising
Rover: Fix SYSID ranges to support GCS display of param correctly
Copter: Fix SYSID ranges to support GCS display of param correctly
DataFlash: try to keep dataflash writes aligned

also rename lastlog.txt to LASTLOG.TXT as NuttX seems to get less
corruption with VFAT filenames that don't need uppercase mappings
Plane: use uppercase names on microSD card where possible
Copter: use uppercase names on SD card where possible
Rover: use uppercase names on SD card where possible
HAL_PX4: try to use uppercase names on NuttX microSD card
PX4: use BOOT.LOG instead of boot.log
HAL_PX4: added support for MTD (FRAM) parameters

this allows us to store parameters and waypoints in FRAM, and
auto-upgrade from microSD
DataFlash: improve reliability of microSD for logs