Fixed thumbnail bug with .tbx lots.

When tilesets are added or removed from TileMetaInfoMgr's list of tilesets,
MapManager emitted the mapFileChanged signal for all .tbx lot maps.  Because
the .tbx didn't actually change, MapImageManager's mapFileChanged slot was
producing a zero-sized map image.  So I added the 'force' parameter to make
sure the map thumbnail is always recreated.
Fixed TileMetaInfoMgr's tilesets not always getting added to the FileSystemWatcher.
Synching some code with WorldEd.
Put up a progress dialog when map files changed on disk.

Without this, the progress dialog may hide/show several times in a row.
Fixed MapManager not emitting mapFileChanged signal unless a map was loaded.

When a MapInfo points to a real file, the file's path is added to FileSystemWatch
even if the map wasn't loaded.  Since MapImageManager uses MapInfo to track
changes to map files, it is important to emit the mapFileChanged signal even
when a map isn't loaded.
Fixed off-by-1 error with the size of .tbx maps in MapInfo.
Fixed error calculating adjacent rectangles for 'Highlight Room under Pointer'.
Clear the building tile selection when switching from tile mode to object mode.
Fixed Tilesets.txt not being written if TileMetaInfoDialog was accessed via BuildingTilesDialog.
BuildingTilesDialog displays the name of a missing tileset rather than "missing".
BuildingTilesDialog redisplays category/furniture tiles when tilesets are added/removed.
Updated *.txt config files.
Center the view when opening a building in BuildingEd.
Added MapImage::isLoaded(), don't display unloaded map thumbnail in the Maps Dock.

If an map image hasn't been loaded by a worker thread yet, don't display the
image in the Maps Doc.  It will be displayed when the mapImageChanged signal
is emitted.
Delete all the image-reader threads when deleting MapImageManager.
MapManager reads only the first 1024 bytes of a map file when getting info.

I *think* the QXmlStreamReader reads the whole file in.
The default Tiles Directory is ../Tiles or ../../Tiles.

Instead of looking only for ../Tiles we also look for ../../Tiles.
Also, the path is cleaned of "..".
Don't display a progress dialog when the current Maps Directory changes.

ZLotManager used to try to reload lot maps when the current directory displayed
in the Maps Dock was changed.
The Maps Dock displays the current path using the platform's separator char.