V1.0.3

1.0.3
* correct default pinmux value for UART and SPI to those functions
* fix string length error in rc_spi_loopback_test
* add minimum realization case for PI and P controller in rc_filter_pid
* fix compass heading in 2 DMP orientation options
* fix uninitialized matrix in rc_altitude example
* fix spi randomly breaking due to non-initialized struct
* small documentation improvements