This also fixes a bunch of bugs where an error during save would
still close the window (rather than cancelling the close action).
Fixes: lp:1785034
* https://bugs.launchpad.net/kicad/+bug/1785034
Put the buttons in platform-compliant order.
Get rid of SaveMultiOptions in favour of repeated standard save
dialogs with a "Apply to all" checkbox.
Fixes: lp:1783444
* https://bugs.launchpad.net/kicad/+bug/1783444