Initial guide deviation check not executed.

This issue is partly a bug, partly a feature request.

1. Bug Report: The initial guide deviation is not always checked at the start of a sequence. In case e.d. a filter change, the check is skipped because the m_State == CAPTURE_CHANGING_FILTER instead of CAPTURE_PROGRESS

2. Feature Request: The guide deviation check should be executed in front of each frame capture and not only at the beginning of a sequence. The rationale behind is that some users experience heavier guiding drift after dithering that indicates settling after dithering isn't completed. To safeguard this it is better if the guide deviation check is executed in front of each frame capture.