Fixed MapComposite not synching layer opacity correctly.

MapComposite::addMap() was setting the opacity of layers in the new map to
match the opacity of its layers, rather than using the mLayerOpacity value
like it should.  Also, it wasn't doing it recursively on submaps of the submap.

When an already-loaded submap was reloaded, the opacity of layers in that map
were being reset to 1.0.

Another issue with CompositeLayerGroup::synch() was that submaps weren't
using the layer name/opacity/visibility of the root map, only the parent
map.
Door and window objects don't replace the wall unless they align with the wall.

Previously, any time a door or window was placed next to a wall, the wall
tile would be replaced to have a hole in it.  That only makes sense if the
door or window is "in" the wall.  When placing a bathroom stall door next
to a wall there shouldn't be a hole in the adjacent wall.
Updated BuildingEd tools doc and FurnitureTool status text.
Re-implemented the "refresh" button on the minimap.
Fixed the minimap not redrawing itself properly when tilesets changed.
Document tab tooltips use QDir::toNativeSeparators().
Added 0_ prefix to the name of the tile layer created with a new map.
Synched a bit of WorldEd-related code.
Hidden layer groups no longer contribute to the bounds of a map.
MapComposite code cleanup (and synching with WorldEd).
Fixed bug with MapComposite::mSortedLayerGroups.

The MapComposite constructor calls addMap() which calls ensureMaxLevels()
which might add new layer groups to mSortedLayerGroups.  Then the constructor
would append all the layer groups *again* to mSortedLayerGroups resulting in
layer groups being listed twice.

I think this bug only affected MapComposite::zOrder(), which means that
when creating map thumbnails of maps with submaps, every tile was painted
twice.  A map being edited wasn't affected because that didn't call addMap().

I only noticed this bug when I changed WorldEd's MapComposite code to use
addMap(), which resulted in duplicate levels being displayed in the Layers
dock of WorldEd.