ENH: Refactored DICOMHeaderPopup and inheriting from ctkDICOMObjectListWidget

• removed unused imports and specified ctk imports explicit

ENH: Fixed typos, parentheses, semicolons, string formatting, settings:

• simplified promptForDatabaseDirectory
• removed unused variables

BUG: fixed loadButton availability in various situations

• taking into account if series are selected, advanced mode is active and if in
  advanced mode loadables are checked

ENH: Refactoring and using of DICOMSendDialog for sending DICOM

• Once a patient, studie, series is selected, it can be send via storescu

ENH: centering DICOMSend progressbar on mainWindow

STYLE: add newline at end of file

From: Steve Pieper <pieper@isomics.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25545 3bd1e089-480b-0410-8dfb-8563597acbee