Fixed rail capacity + added mouse wheel scrolling — 1941 - Operation Barbarossa Steam update #1294926

Fixed rail capacity calculation. Now it correctly counts Soviet capacity to be 8 units of any type, meaning 8 units in total, not 8 units of every type (24 units in total) as it was before. Also for Axis units it now correctly allows 3 Corps units or 1 Group or 1 Army, where it previously allowed 3 Corps, 1 Group and 1 Army. Axis can also now utilize the special Finnish rail capacity in addition to the normal Axis rail capacity. Note: If a Finnish unit could use both the Finnish capacity and the Axis normal capacity, then it uses the Finnish capacity as long as it is available. In addition to previous scrolling methods (mini-map + scroll bars), the main map can now be scrolled with mouse wheel also. Rolling the wheel normally scrolls the map vertically, whereas rolling the wheel while holding the Shift key down scrolls the map horizontally.