Updated to MonoGame 3.6 + Directory refactor

- Barotrauma's projects are in the Barotrauma directory
- All libraries are in the Libraries directory
- MonoGame is now managed by NuGet, rather than referenced from the installed files (TODO: consider using PCL for easier cross-platform development?)
- NuGet libraries are not included in the repo, as getting the latest versions automatically should be preferred
- Removed Content/effects.mgfx as it didn't seem to be used anywhere
- Removed some references to Subsurface directory
- Renamed Launcher2 to Launcher

Barotrauma/BarotraumaShared/Content/Items/Ladder/ladder.xml

@@ -0,0 +1,11 @@
+<Item
+  name="Ladder"
+  resizevertical="true">
+
+
+  <Sprite texture ="ladder.png" depth="0.05"/>
+
+  <Ladder canbeselected = "true"/>
+
+  <trigger x="-40" y ="20" width="90"/>
+</Item>