improved handling of claimlistview's "add" row

When adding rows, this will now also work without necessarily having a "add" row. Since this is
properly working now, we can also remove the code creating a dummy "add" row for property
sections of deleted properties.
Also removed code (which has not really been working anyhow) which would add 'wb-last' and
'wb-first' classes to the rows.

Change-Id: I9b81093215f495da42517689cb480df2bf181d64
Merge "improved handling of claimlistview's "add" row"