fix: Fixes localization corner cases with OPL (#1050)

## Changes
- [X] Adds OPL convenience methods
    - `opl.Add(cliloc, value)` and `opl.Add(value)` - value as an integer or string works just like `opl.Add(cliloc, $"{value}")`
    - `opl.AddLocalized(cliloc, clilocValue)` - works the same as `opl.Add(cliloc, $"#{clilocValue}");`
- [X] Simplifies basic `list.Add()` situations
- [X] Changes cliloc as an argument so it works with custom IPropertyList implementations (HTML)
- [X] Fixes plants so they support the old localization and new (changed in 7.0.12.0+)
- [X] Exposes more methods to override for Item to make creating custom OPL possible.

## Important Notes
* Using a ternary as an argument, like this `opl.Add(number, showType ? $"{type}\t{value}" : $"{value}");` _will not use the correct string interpolation_. This means if you use a custom PropertyList (for HTML or some other purpose), the property list won't be localized properly.
* All localization values must be interpolated, even if they are literal strings, or integers. Example: `opl.Add(number, $"{"Charges"}\t{m_Charges}");` is correct. Using the following: `$"Charges\t{m_Charges}"` will not work for custom PropertyList implementations!

Projects/UOContent/Multis/Houses/BaseHouse.cs

@@ -3721,12 +3721,17 @@ namespace Server.Multis
                     ref ySouth
                 );
 
-                var location =
-                    valid ? $"{yLat}° {yMins}'{(ySouth ? "S" : "N")}, {xLong}° {xMins}'{(xEast ? "E" : "W")}" : "unknown";
-
                 list.Add(1061112, Utility.FixHtml(houseName)); // House Name: ~1_val~
                 list.Add(1061113, owner);                      // Owner: ~1_val~
-                list.Add(1061114, location);                   // Location: ~1_val~
+                if (valid)
+                {
+                    // Location: ~1_val~
+                    list.Add(1061114, $"{yLat}° {yMins}'{(ySouth ? "S" : "N")}, {xLong}° {xMins}'{(xEast ? "E" : "W")}");
+                }
+                else
+                {
+                    list.Add(1061114, "unknown"); // Location: ~1_val~
+                }
             }
 
             public override void Serialize(IGenericWriter writer)

Projects/UOContent/Multis/Houses/HouseSign.cs

@@ -83,7 +83,7 @@ namespace Server.Multis
                         level = DecayLevel.IDOC;
                     }
 
-                    list.Add(1062028, $"#{1043009 + (int)level}"); // Condition: This structure is ...
+                    list.AddLocalized(1062028, 1043009 + (int)level); // Condition: This structure is ...
                 }
             }
         }