Create installer with qmake

This is seriously flawed. makensis is run twice for some reason. I also
noticed that the data and xslt directories under packaging/windows aren't
created when running make install. Running
	make -f Makefile.Release install_marbledir install_deploy
works, but obviously this should be taken care of by the dependency.

The installed binary under Windows is not finding its icon, the
translations are missing... lots of work left to do here.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't force the DiveListView to be a tree when reloading

We should keep whatever view the user last used.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Remember the column we are sorting by

A call to DiveListView::reload always reset our sortcolumn to be 0.
Instead we are tracking the correct sort column and sort direction.

This also removes an obsolete private member that was unused.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix dive merging

When merging dives, the indices of the following dives change - so we need
to adjust the variable used in the for_each loop.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Show a different message when editing more than one dive

I still wonder if we have all the semantics correct for multi dive
editing. This will need more testing.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>