Add missing setX and X methods on CPControl.

Moved the logic for setStringValue to setObjectValue on CPTextField.
Now, all setX's call setObject.  We store native objects, and cast
to the appropriate type in the getter methods.

AppKit/CPTextField.j

@@ -432,23 +432,28 @@ var _CPTextFieldSquareBezelColor    = nil;
         return [[self class] _inputElement].value;
 #endif
 
-    return [_value string];
+    return [self stringValue];
 }
 
 /*
-    Sets the string the text field.
+    @ignore
 */
-- (void)setStringValue:(CPString)aStringValue
+- (void)setObjectValue:(id)aValue
 {
-    _value = aStringValue;
+    [super setObjectValue:aValue];
     
 #if PLATFORM(DOM)
-    var cssString = _value ? [_value cssString] : @"";
+    var displayString = "";
+
+    if ([aValue respondsToSelector:@selector(string)])
+        displayString = [aValue string];
+    else
+        displayString += aValue;
 
     if (CPFeatureIsCompatible(CPJavascriptInnerTextFeature))
-        _DOMTextElement.innerText = cssString;
+        _DOMTextElement.innerText = displayString;
     else if (CPFeatureIsCompatible(CPJavascriptTextContentFeature))
-        _DOMTextElement.textContent = cssString;
+        _DOMTextElement.textContent = displayString;
 #endif
 }