UDBScript: Map class: the getSidedefsFromSelectedLinedefs() method now correctly only returns the Sidedefs of selected Linedefs in visual mode (and not also the highlighted one)
UDBScript: Map class: added a new getSidedefsFromSelectedOrHighlightedLinedefs() method as the equivalent to the other getSelectedOrHighlighted*() methods
UDBScript: Sector class: added new floorSelected, ceilingSelected, floorHighlighted, and ceilingHighlighted properties. Those are mostly useful in visual mode, since they always return true when the Sector is selected or highlighted in the classic modes. The properties are read-only
UDBScript: Sidedef class: added new upperSelected, middleSelected, lowerSelected, upperHighlighted, middleHighlighted, and lowerHighlighted properties. Those are mostly useful in visual mode, since they always return true when the parent Linedef is selected or highlighted in the classic modes. The properties are read-only
UDBScript: added new example to apply textures for floor/ceiling and upper/middle/lower texture for selected map elements
UDBScript: updated documentation
