build: add Raspberry Pi toolchain
build: add navio build target
AP_HAL: add configuration for HAL_BOARD_SUBTYPE_LINUX_NAVIO
AP_Baro_MS5611: add address switch for Navio board
HAL_Linux: Add SPI configuration for Navio

This changes the SPI bus number to be zero based on Linux
AP_InertialSensor: Use MPU9250 DRDY pin only on boards that support it
AP_Notify: Add dummy LED configuration for Navio
StorageManager: first version of storage management library

used to divvy up eeprom/fram and allow for expandable storage
StorageManager: added example sketch

note: this destroys the data
build: added subtypes for all boards
SITL: allow for different storage sizes
AP_HAL: ensure we have subtypes for all boards
AP_Param: convert to using StorageManager
AP_Rally: convert to using StorageManager
AP_Mission: convert to using StorageManager
AP_Limits: convert to using StorageManager
AntennaTracker: convert to using StorageManager
Plane: convert to using StorageManager
Copter: convert to using StorageManager
Rover: convert to using StorageManager