NvServices refactoring (#120)

* Initial implementation of NvMap/NvHostCtrl

* More work on NvHostCtrl

* Refactoring of nvservices, move GPU Vmm, make Vmm per-process, refactor most gpu devices, move Gpu to Core, fix CbBind

* Implement GetGpuTime, support CancelSynchronization, fix issue on InsertWaitingMutex, proper double buffering support (again, not working properly for commercial games, only hb)

* Try to fix perf regression reading/writing textures, moved syncpts and events to a UserCtx class, delete global state when the process exits, other minor tweaks

* Remove now unused code, add comment about probably wrong result codes

Ryujinx.Core/Gpu/NvGpuEngine.cs

@@ -0,0 +1,11 @@
+namespace Ryujinx.Core.Gpu
+{
+    enum NvGpuEngine
+    {
+        _2d     = 0x902d,
+        _3d     = 0xb197,
+        Compute = 0xb1c0,
+        Kepler  = 0xa140,
+        Dma     = 0xb0b5
+    }
+}