Add support for [CallerMemberName]

[Philip Lee]

Caliburn.Micro has added support for CallerMemberName. Synchronize your implementation with Caliburn.Micro. e.g. something like:

        /// <summary>
        /// Notifies subscribers of the property change.
        /// </summary>
        /// <param name = "propertyName">Name of the property.</param>
#if NET || SILVERLIGHT
        public virtual void NotifyOfPropertyChange(string propertyName) {
#else
        public virtual void NotifyOfPropertyChange([System.Runtime.CompilerServices.CallerMemberName] string propertyName = null) {
#endif
            if (IsNotifying) {
                Execute.OnUIThread(() => OnPropertyChanged(new PropertyChangedEventArgs(propertyName)));
            }
        }