Added SmartText and inheritors SmartPlainText and SmartEmbedText which will replace CREmbed in the future

src/NadekoBot/Common/SmartText/SmartTextEmbedFooter.cs

@@ -0,0 +1,12 @@
+using Newtonsoft.Json;
+
+namespace NadekoBot
+{
+    public class SmartTextEmbedFooter
+    {
+        public string Text { get; set; }
+        public string IconUrl { get; set; }
+        [JsonProperty("icon_url")]
+        private string Icon_Url { set => IconUrl = value; }
+    }
+}