Figure out what to do about sdi_title vs. title.

[mcdonc]

Should it be ``title`?

[cguardia]

@mcdonc do you remember what's this about?

[tseaver]

ISTM that bjects which have a real title property should use it by default for the sdi_title. I think Folder should have a title by default, as well (the add view could title-case the slug if not provided).