Initial cPlayerState and cPlayerSelection code.

/biomeinfo uses the new player state.
Fixed selection Y coords.
Using wand selection reports the set coords.

Also the //size command uses cPlayerState.
Added initial UndoStack implementation.
//set command uses new architecture.
//Replace uses new architecture.
cPlayerState / cPlayerSelection handle the WECUI.
//faces command uses new architecture.
//walls command uses new architecture.

Also fixed //faces replacing everything with air.
//undo command uses new architecture - cUndoStack.
//redo command uses new architecture - cUndoStack.

Fixes #20 (multi-level undo / redo).
Fixes #21 (world dependence for undo / redo).
CheckAreaCallbacks() uses a cCuboid for the affected region coords.
Merge remote-tracking branch 'origin/master' into PlayerState
//expand now uses the new architecture.
Better description for the cPlayerSelection:Expand function.
The NotifySelectionChanged only gets called once.
Clipboard uses the new architecture.
//rotate command uses new architecture.
Fixed minor bugs.
Info: Using subcommand aliases instead of info-table copies.
Fixed player selection size description.