Item validation can result in a wrong lowerName.

When an item is validated, its name can be automatically changed to make it unique.  We store a lowerName value for the name, but this was calculated before the name change rather than after.  Also, added a guard in createItem to avoid a description that was None and to strip whitespace from the name and description as the item is created, rather than just on validation.
More guards against bad item names and descriptions.
Merge pull request #471 from girder/item-lowername-doesnt-match

Item validation can result in a wrong lowerName.