Add additional decoupling for the IMU

[juchong]

Resetting the IMU causes VDD to fluctuate significantly. More decoupling should be added to lessen this behavior.

[ajn96]

@juchong

I set up Vdd monitoring and use it to compensate the temp sensor reading. This makes the temp sensor fairly noisy, but it now no longer shifts when the supply voltage shifts.

[ajn96]

Added a decimation filter to the temp sensor output to make it look a little cleaner. Can still see the noise from a messy supply being multiplied into the temp measurement, but it's not as bad.

[ajn96]

This has been incorporated into the rev C board design (100 puf caps decoupling IMU supply)