Improve user experience while importing data

[fedorov]

Two options (later add icons?):

1. import into DB only
2. import & load

Import and load:

1. index the directory:
   indexer = ctk.ctkDICOMIndexer(); indexer.addDirectory(slicer.dicomDatabase, inputStudyDir)
2. get the list of loadables and examine using each one (?)
   plugin = slicer.modules.dicomPlugins'DICOMScalarVolumePlugin'
   svs = plugin.examine([filenames])
   volume = plugin.load(svs[0])

[mehrtash]

Fixed at: c51eace