Log Replay: Fix for random crash involving not checking array size before accessing
Log Replay: Improved speed and position modifiers as well as cpu usage.

The Log replay thread now runs its own mavlink parser, which offloads
some of the CPU usage from the UI thread. This should make the UI a bit
more responsive when running the replay at higher speeds.

The position display has also been changed to be a user-settable slider,
for allowing the user to jump around in the log file. This will make
graphs look a bit odd if the user is constantly jumping, but that is to be
expected.
Status Bar: Removed hardcoded stylesheet for QGCStatusBar

TLog replay controls will now follow the current stylesheet colors properly.
Log Replay: Improvments to the UI, as well as the backend for mavlink handling

Changed the slider for speed to 5 buttons, 0.75X, 1X, 1.5X, 2X, and 5X for
log replay speed control.

Also fixed a bug where not all mavlink messages were being recognized by
the graph view, and none were being recognized by the Mavlink inspector
during log playback
Log replay: Added 10x speed button, and cleaned up unneeded code