Water flow logic tweaking:

- Less fluctuation, water doesn't constantly flow back and forth through gaps.
- Flowing water pushes characters around much more heavily, and the force is applied to the collider in addition to the limbs.
- Vertical gaps don't push characters up/down unless the character is roughly above/below the gap.

+ Renamed some fields in the hull and gap classes (Volume -> WaterVolume, FullVolume -> Volume, public fields start with a capital letter)

Barotrauma/BarotraumaShared/Source/Map/WayPoint.cs

@@ -356,7 +356,7 @@ namespace Barotrauma
                         
             foreach (Gap gap in Gap.GapList)
             {
-                if (!gap.isHorizontal) continue;
+                if (!gap.IsHorizontal) continue;
                 
                 //too small to walk through
                 if (gap.Rect.Height < 150.0f) continue;
@@ -381,7 +381,7 @@ namespace Barotrauma
 
             foreach (Gap gap in Gap.GapList)
             {
-                if (gap.isHorizontal || gap.IsRoomToRoom) continue;
+                if (gap.IsHorizontal || gap.IsRoomToRoom) continue;
 
                 //too small to walk through
                 if (gap.Rect.Width < 100.0f) continue;