BUG: Fixed issue of DICOM browser not closed after loading a volume

Browser was not closed after loading a volume even if "Persistent" checkbox was unchecked.

Also added a settings (DICOM/BrowserPersistent) to remember the checkbox setting.

From: Andras Lasso <lasso@queensu.ca>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23550 3bd1e089-480b-0410-8dfb-8563597acbee