Fixed severe lock-up after finishing dragging many vertices/linedefs/sectors in Classic modes.
Updated documentation ("Synchronizing camera position").
Added, Game configurations: added "thingclasshelp" property. It's used to open a website when thing class name is clicked in the Thing Edit form.
Changed, "Raise/Lower sector to nearest" action: 3d floors are now taken into account when using the action on things.
Updated documentation.
Increased maximum zoom level in Classic modes to 3000%.
Added "1 mp" option in grid size menu.
Added "400%" option in zoom menu.
Renamed "Toggle GZDoom rendering effects" action to "Toggle Geometry Effects".
Sync camera position: Visual Camera height is now changed only if camera is above or below current sector.
Classic modes: view was not redrawn after "Test map from current position" action.
"Test map from current position" action: incorrect player start was used when a map had several Player 1 Start things.
