Add being able to override the one-way recolor

Disabling the one-way recolor if assets are mounted is needed to make
existing levels not look bad, but what about levels that want to use the
recolor anyway?

The best solution here is to just introduce another bool into the XML,
and make the re-color opt-in and only present if assets are mounted if
that tag is present.

desktop_version/src/editor.cpp

@@ -398,6 +398,8 @@ void editorclass::reset()
 
     ghosts.clear();
     currentghosts = 0;
+
+    onewaycol_override = false;
 }
 
 void editorclass::gethooks()
@@ -1708,6 +1710,11 @@ bool editorclass::load(std::string& _path)
                 {
                     website = pText;
                 }
+
+                if(pKey == "onewaycol_override")
+                {
+                    onewaycol_override = atoi(pText);
+                }
             }
         }
 
@@ -1993,6 +2000,13 @@ bool editorclass::save(std::string& _path)
     meta->LinkEndChild( doc.NewText( website.c_str() ));
     msg->LinkEndChild( meta );
 
+    if (onewaycol_override)
+    {
+        meta = doc.NewElement( "onewaycol_override" );
+        meta->LinkEndChild( doc.NewText( help.String(onewaycol_override).c_str() ));
+        msg->LinkEndChild( meta );
+    }
+
     data->LinkEndChild( msg );
 
     msg = doc.NewElement( "mapwidth" );