Fixes and features

Added text to explain that spacebar captures the current frame
Capturing another picture will not start unless the current one has
finished encoding; this way there will be no more garbled frames
Clicking the OK button would previously trigger a camera reconnect even
with only the quality being changed because of some faulty camera
switching logic
Removed timing function from the worker class
Reduced ammount of messaging between worker and main, as well as debug
trace's
Renamed some variables for clarity