Includes a number of small DataForm fixes and some fixes to Product imports.

Changelog:

 - fixed: failure when submitting a dataform that sends mail with an empty file field
 - fixed: DataForm ignores height on textarea fields
 - fixed: DataForm doesn't keep posted values properly when data fails validation
 - fixed: some default assets have ids shorter than 22 characters
 - fixed: ~~~ showing up on my site.
 - fixed: Shelf/Product import export does not work
 - fixed: Shelf/Product import does not work with windows files
 - fixed: Can no longer buy badges from receipt or direct link page if quantity is empty
 - fixed: DataForm entry table isn't properly indexed
 - fixed: DataForm can't export fields containing newlines
 - fixed: Documentation for DataForm and Thingy "Possible Values" field
 - fixed: Shortcuts includes HTML head data twice
 - fixed: UserList templates use incorrect variable names