adding ExtractImu to logtool

- added an ExtractImu option to logtool and implemented it to take a logfile and extract a series of CSV files with data from each of the sensors that might be onboard the IMU.
- squelched an error message complaining about Protobuf definitions having been changed when they in fact haven't.
- tested on two separate logfiles successfully (ximea-phi-calib4 that contained image and IMU data, and another random dataset of walking around in a loop).