Restore the HFR etc statistics.

Somehow the HFR and related statistics that were displayed in Analyze were lost. This restores that.

Details.

In the current code, star detection for a captured image (when the AutoHFR feature is checked) happens for the fitsview, but it happens too late for capture's emit captureComplete(..., hfr, ...) signal. This wasn't the case a while back, but I assume with some recent re-structuring, the code in fitstab that previously triggered it in time got delayed. So now, when capture tries to retrieve the hfr, it gets -1 (as it doesn't compute it, just retrieves it).

This MR causes capture to actively compute star detection, if it hasn't already been done, so that the HFR can be retrieved.

It's certainly possible that the right place for this computation is inside fitsdata.cpp. I know that @mutlaqja is looking into separating fitsdata and fitsdisplay, and modifying this could be part of that future change.