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

Libraries/Lidgren.Network/Documentation/Improvements.txt

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+
+Improvements over last version of library:
+
+* New delivery type: Reliable sequenced (Lost packets are resent but late arrivals are dropped)
+* Disconnects and shutdown requests are now queued properly, so calling shutdown will still send any queued messages before shutting down
+* All messages are pooled/recycled for zero garbage
+* Reduced CPU usage and lower latencies (in the <1 ms range, but still) due to better socket polling
+* All public members of NetPeer/NetConnection are completely thread safe
+* Larger number of delivery channels
+* More exact roundtrip measurement
+* Method serialize entire objects via reflection
+* Unique identifier now exists for all peers/connections
+* More flexible peer discovery; filters possible and arbitrary data can be sent with response
+* Much better protection against malformed messages crashing the app
+
+API enhancements:
+* NetPeerConfiguration immutable properties now locked once NetPeer is initialized
+* Messages cannot be send twice by accident
+* Impossible to confuse sending and receiving buffers since they're different classes
+* No more confusion if user should create a buffer or preallocate and reuse
+
+