Added icons to main menu

Added icons to entries and groups with a mapping
Created a Converter to handle pluralization
Several UI enhancements

ModernKeePass/Converters/PluralizationConverter.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using Windows.UI.Xaml.Data;
+
+namespace ModernKeePass.Converters
+{
+    public class PluralizationConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, string language)
+        {
+            var pluralizationOptionString = parameter as string;
+            var pluralizationOptions = pluralizationOptionString?.Split(new[] { "," }, StringSplitOptions.RemoveEmptyEntries);
+            if (pluralizationOptions == null || pluralizationOptions.Length != 2) return string.Empty;
+            var count = value is int ? (int) value : 0;
+            var text = count == 1 ? pluralizationOptions[0] : pluralizationOptions[1];
+            return $"{count} {text}";
+        }
+
+        // No need to implement this
+        public object ConvertBack(object value, Type targetType, object parameter, string language)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}