LP-597 Progress bar for GCS log replay - add progress bar and a stop button

- Added stop button:
  - start: starts from 0 position after stop signal, resumes from current position after pause signal.
  - pause: freezes at current position, also freezes scopes.
  - stop: stops replay and resets start position to 0 (does not close the logfile)
- Creates an index of the timestamp positions in the logfile for quick seeking to the target position in the log.
- Start, End and current position timestamps are visible in the GUI below the position slider.
- Determine replay position by moving the position slider
- Update position label while changing position bar
- Speed widget: lowest multiplier is now 0.1 instead of 0.
  Only set one decimal of precision.
  More decimals seem useless at this time.

Author: dr-oblivium