Fixed BuildingEd tool not being remembered when switching edit mode.
Restore minimized BuildingEd window in confirmSave().
Moved a bunch of code from BuildingEditorWindow to new CategoryDock class.
QtCreator-like overhaul of BuildingEd GUI.

BuildingEd had object-editing mode and tile-editing mode.  Each mode has
its own toolbar and dock widgets.  Switching modes didn't look nice because
of the toolbar/dock widgets being hidden/shown.

Following QtCreator's example, each mode now has its own embedded QMainWindow
with its own toolbar and dock widgets.  A QStackedWidget is used to cleanly
switch editing modes.
Fixed undo/redo crash with SelectMoveRoomsTool.

Wasn't checking if the tool was the current one.
This is a bit weird, the current selection should probably be saved in the
document like the tile/object selections are.
Split object edit mode into separate modes.

Instead of using a QStackedWidget to toggle the iso/ortho modes, split them
into their own modes.  It's a bit weird because they now have separate
toolbars and docks.

Also added ModeManager to handle switching modes cleanly.
Added FancyTabWidget from QtCreator to BuildingEd.
Added mode icons, WelcomeMode to BuildingEd.

Also, try to keep the iso-object-view and iso-tile-view scale/position in
sync.
Start BuildingEd in WelcomeMode & disable other modes when no documents are open.
Fixed object names and settings handling in various BuildingEd docks.
Fixed BuildingTilesetDock not responding to changes in the current document.
Added keyboard shortcuts to switch BuildingEd modes.

The function keys F1-F4 switch between modes.
Fixed and organized BuildingEd QSettings stuff.
Fixed remembering/restoring the current tool when switching modes in BuildingEd.
Renamed "Clean-up" to "Remove unused entries" in BuildingEd category dock.
Added View > Views menu to hide/show BuildingEd toolbars and docks.
Fixed CategoryDock::resetUsedTiles() removing used building wall grime tile.
Changed BuildingEd's "Floor 1/N" label to a button that displays the Floors Dialog.
Fixed compilation under g++.

It is incredible MSVC choked down some of this code.
Added status text to BuildingEd's PickTileTool.