coherent wavemeter doesnt crashes the gui. Now it closes if error occurs, and there is a reconnection button

Two small bugs solved: spinbox blocked only if scan starts, and when canceling the roi window gui doesn't crash.

webcams and webcamROI added. Still this last needs to be integrated to the GUI, but it works on its own.

Small change to make scans works properly. Now they can never escape the scan interval and they dont run if the spinbox value is outisde region of scan. Also, they start and stop softly.

Scans functions corrected, now the time step is 5ms and that way works fine for now. Also dark theme option enabled.