Refactoring HOS folder structure (#771)

* Refactoring HOS folder structure

Refactoring HOS folder structure:

- Added some subfolders when needed (Following structure decided in private).
- Added some `Types` folders when needed.
- Little cleanup here and there.
- Add services placeholders for every HOS services (close #766 and #753).

* Remove Types namespaces

Ryujinx.HLE/HOS/Services/Fs/ResultCode.cs

@@ -0,0 +1,16 @@
+namespace Ryujinx.HLE.HOS.Services.Fs
+{
+    enum ResultCode
+    {
+        ModuleId       = 2,
+        ErrorCodeShift = 9,
+
+        Success = 0,
+
+        PathDoesNotExist  = (1    << ErrorCodeShift) | ModuleId,
+        PathAlreadyExists = (2    << ErrorCodeShift) | ModuleId,
+        PathAlreadyInUse  = (7    << ErrorCodeShift) | ModuleId,
+        PartitionNotFound = (1001 << ErrorCodeShift) | ModuleId,
+        InvalidInput      = (6001 << ErrorCodeShift) | ModuleId
+    }
+}