OP-1531 Filter temperatures for gyro and accel calibration. calculate new bias every 30 samples
OP-1531 - Add temperature filtering for baro compensation
OP-1535 - change sensor rate to 1KHz with software downsample to 500Hz

Allow per board SPI prescaler settings
OP-1535 - Fixes CC3D sensor SPI configuration
OP-1535 - Refactor MPU6k driver to allow direct and fifo access based on configuration
OP-1535 - Some optimizations for attitude module
OP-1535 - SPI:Use pio for small blocks
OP-1538 Added description to fields in the UAVObject description files.
Descriptions can be added to fields either as attributes or child nodes.
Descriptions are not mandatory at this stage.
The description shows up when hovering over objects and fields in the UAVObject browser.

Added example descriptions to a few fields in the UAVO descriptor files.
OP-1513 - Fix time constants, set initial temperature as first sample value
OP-1538 Added saving of splitter sizes.
OP-1538 Added some Vogon poetry.
Merge remote-tracking branch 'origin/next' into thread/OP-1538_Embedded_Documentation
OP-1538 Added table format + colors
OP-1535 - Add board specific sensor update rate constant
OP-1535 - uses union in fast_invsqrt
OP-1538 UavObjectDefinition typos
OP-1538 All cells with color
OP-1538 Changed the way splitter state is changed.
Fixed some formatting colors.
Merge remote-tracking branch 'origin/laurent/OP-1538_Embedded_Documentation' into thread/OP-1538_Embedded_Documentation
OP-1538 Small formatting changes.