BUG: #3014 fix databundle save/restore for dicom volumes

Fix a hole in the logic where a dicom volume would have a storage
node allocated, but the storage type would not be correctly defined
so the temp save path would not work.  Plus the default name
would be set to an invalid filename since dicom volume nodes
have a colon in the string by default.  Now these files are given
a default extension type (.nrrd for scalar volumes) and the names
are percent-encoded to avoid bad file name issues.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22143 3bd1e089-480b-0410-8dfb-8563597acbee