Interactive vs programmatical use

When preview is running, by default TVideoGrabber restarts preview automatically each time a setting that requires restarting preview is modified. This behavior avoids having to call StartPreview when adjusting video properties. However it can cause useless preview restarts e.g. if several properties are set programmatically when preview is running. In this case disable AutoRefreshPreview to disable this feature. Then, the changes will be applied only when StartPreview will be invoked again.