Fix warnings.

Interop/DetectOS.cs

@@ -84,11 +84,11 @@ namespace Aaru.CommonTypes.Interop
                     var principal = new WindowsPrincipal(user);
                     isAdmin = principal.IsInRole(WindowsBuiltInRole.Administrator);
                 }
-                catch(UnauthorizedAccessException ex)
+                catch(UnauthorizedAccessException)
                 {
                     isAdmin = false;
                 }
-                catch(Exception ex)
+                catch(Exception)
                 {
                     isAdmin = false;
                 }

Metadata/Dimensions.cs

@@ -38,6 +38,8 @@
 
 using Schemas;
 
+#pragma warning disable 612
+
 namespace Aaru.CommonTypes.Metadata
 {
     public static class Dimensions

Metadata/MediaType.cs

@@ -36,6 +36,7 @@
 // Copyright © 2011-2020 Natalia Portillo
 // ****************************************************************************/
 
+#pragma warning disable 612
 namespace Aaru.CommonTypes.Metadata
 {
     public static class MediaType