Refactored the LogCompressor. It wasn't properly handling certain message logging files that mixed messages (Issue #70).
One note is that this logger should work correctly as I've tested it, but could have some edge cases. It is pickier about the file format that it will sparse, but I don't know if the error-checking stuff from the old code would have actually worked. This can also be easily re-added.

This code is also much faster than the old stuff. From what I could tell it scanned through the log file at least twice, I think three times. It also copied a lot of data into memory instead of reading, processing, and writing one line at a time, so memory use should be much lower. Some memory leaks from the old code were also refactored out, so lifetime memory use should be down.

Fixed a couple of uninitialized arrays within the MAVLinkDecoder. It would result in weird time values in some data logging instances.

Replaced the autopilot-specific inclusion of MAVLink to be more generic. Now if you have no actual QGC modifications to make and just want your messages to be available for viewing/logging you can just create the user_config.pri file and override MAVLINK_CONF.

Also changed calculateRegression(...) to return a bool, as that's all it needs.

Fixed a stack overflow bug when using the regression fitting command in logfile plot. Solution involved just allocating on the heap instead of the stack.

Added a check for a division by zero in AbstractCalibrator::logAverage(). This was causing a crash when attempting a calibration when there's no RC data being received.

Modified the Linechart widget so that the "Show units" button is under the "Curve Selection" frame, which is what it actually modifies.
Also moved all of the UI that was under the "Curve Selection" to inside of it at the bottom so that the grouping of UI elements is more coherent.

Added text (component id) to cone/circle symbol symbolizing pose data from that component in 3D view.

Unified all object selections in 3D view via right-mouse-click, and added mouse-based terrain translation/rotation.