Added magnetic output functions
Cleaned SDK directory structure

- Got rid of Ardusat_ prefixes for third party libraries leveraged by
the SDK in favor of utility/ subdirectory.
- Consolidated includes more sensibly.
Fixed up toCSV functions, bugs, and reduced RAM footprint.

- Fixed existing bugs with toCSV functions in SDK
- Fixed orientationToJSON buffer overflow bug
- Updated example sketch to use 9dof specific toJSON functions
- Added RAM measurement library to utilities
- moved JSON formatting to flash for better RAM footprint
- Refactored drivers library for better RAM and fix bugs
- Removed unnecessary parts of data structure header
- Refactored 9DOF read functions to remove RAM intensive Adafruit drivers
SD Card data write capabilities using SdFat Library.

- Uses modified SdFat Library (https://github.com/greiman/SdFat)
- Use the SD card library buffer for our output buffer when possible to
  conserve RAM
- 8 bit variable for write buffer length
- Write data in CSV or binary formats
Changed to saving floating point values in binary format rather than in conversions
Demo utility to decode binary data log files and re-write as CSV
Updated README & added SD card example
Merge branch 'write-data'