Colors Fix, Perf Improvement, Thread Safety

-Fixes issues with colors not parsing correctly. Saving an SvgDocument
resulted in RGB color values being converted to well known color names.

-Compile regex statements to improve performance.

-Make rendering a document threadsafe.

Source/Painting/SvgColourConverter.cs

@@ -115,7 +115,7 @@ namespace Svg
             if (destinationType == typeof(string))
             {
                 var colour = (Color)value;
-                return ColorTranslator.ToHtml(colour);
+                return "#" + colour.R.ToString("X2", null) + colour.G.ToString("X2", null) + colour.B.ToString("X2", null);
             }
 
             return base.ConvertTo(context, culture, value, destinationType);

Source/Paths/SvgPathBuilder.cs

@@ -276,7 +276,7 @@ namespace Svg
 
         private static IEnumerable<float> ParseCoordinates(string coords)
         {
-            var parts = Regex.Split(coords.Remove(0, 1), @"[\s,]|(?=(?<!e)-)");
+            var parts = Regex.Split(coords.Remove(0, 1), @"[\s,]|(?=(?<!e)-)", RegexOptions.Compiled);
 
             for (int i = 0; i < parts.Length; i++)
             {

Source/SvgElementFactory.cs

@@ -167,30 +167,34 @@ namespace Svg
         }
 
         private static Dictionary<Type, Dictionary<string, PropertyDescriptorCollection>> _propertyDescriptors = new Dictionary<Type, Dictionary<string, PropertyDescriptorCollection>>();
+        private static object syncLock = new object();
 
         private static void SetPropertyValue(SvgElement element, string attributeName, string attributeValue, SvgDocument document)
         {
             var elementType = element.GetType();
 
             PropertyDescriptorCollection properties;
-            if (_propertyDescriptors.Keys.Contains(elementType))
+            lock (syncLock)
             {
-                if (_propertyDescriptors[elementType].Keys.Contains(attributeName))
+                if (_propertyDescriptors.Keys.Contains(elementType))
                 {
-                    properties = _propertyDescriptors[elementType][attributeName];
+                    if (_propertyDescriptors[elementType].Keys.Contains(attributeName))
+                    {
+                        properties = _propertyDescriptors[elementType][attributeName];
+                    }
+                    else
+                    {
+                        properties = TypeDescriptor.GetProperties(elementType, new[] { new SvgAttributeAttribute(attributeName) });
+                        _propertyDescriptors[elementType].Add(attributeName, properties);
+                    }
                 }
                 else
                 {
                     properties = TypeDescriptor.GetProperties(elementType, new[] { new SvgAttributeAttribute(attributeName) });
-                    _propertyDescriptors[elementType].Add(attributeName, properties);
-                }
-            }
-            else
-            {
-                properties = TypeDescriptor.GetProperties(elementType, new[] { new SvgAttributeAttribute(attributeName) });
-                _propertyDescriptors.Add(elementType, new Dictionary<string, PropertyDescriptorCollection>());
+                    _propertyDescriptors.Add(elementType, new Dictionary<string, PropertyDescriptorCollection>());
 
-                _propertyDescriptors[elementType].Add(attributeName, properties);
+                    _propertyDescriptors[elementType].Add(attributeName, properties);
+                } 
             }
 
             if (properties.Count > 0)