Instead of laborously calculating which properties have changed under
which circumstances, we can just connect the signals of dependent
properties. This will give us a few false positive signals at a greatly
reduced risk of missing some actual change. Also, the number of expanded
and collapsed rows will always be determined by the content of the
model. We don't need separate signals for those.
Change-Id: Id8495ee525a91405b039fd032509afa125f96412
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
c679b3202a