BUG: #2990 use conventional layout if saved layout not available

When a module or extension creates a custom layout the number (say, 100)
is saved in the settings file and slicer tries to restore that
on the next start up.  However these layouts can be transient creations
and won't be available at startup.  This patch improves handling of
that case - rather than printing a warning and showing a blank screen, the
program now starts with the regular layout which leads to less
user confusion.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22142 3bd1e089-480b-0410-8dfb-8563597acbee
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