[c++/m] Refactor value fields

Closes #144

Removes value fields checksum, encoder, filename
and reference from C++ and Matlab.

Author: mpsonntag

+nix/Property.m

@@ -52,10 +52,6 @@
             end
 
             nix_mx('Property::updateValues', obj.nix_handle, values);
-
-            dispStr = 'Note: nix only supports updating the actual value at the moment.';
-            dispStr = [dispStr, char(10), 'Attributes like uncertainty or checksum cannot be set at the moment.'];
-            disp(dispStr);
         end
 
         function c = value_count(obj)

src/nixproperty.cc

@@ -41,14 +41,10 @@ namespace nixproperty {
 
             nix::Value pr = vals[i];
 
-            struct_builder sb({ 1 }, { "value", "uncertainty", "checksum", "encoder", "filename", "reference" });
+            struct_builder sb({ 1 }, { "value", "uncertainty" });
 
             sb.set(make_mx_array(pr));
             sb.set(pr.uncertainty);
-            sb.set(pr.checksum);
-            sb.set(pr.checksum);
-            sb.set(pr.filename);
-            sb.set(pr.reference);
 
             mxSetCell(lst, i, sb.array());
         }