Scanner Performance Improvements (#1774)

* Refactored the Genre code to be faster and used a dictonary to avoid some lookups. May fix the rare foreign constraint issue.

* Refactored tag to the same implementation as Genre. Ensure when grabbing tags from ComicInfo, we normalize and throw out duplicates.

* Removed an internal "external" field that was planned for Genres and Tags, but now with new plugin architecture, not needed.

API/Services/Tasks/Scanner/Parser/Parser.cs

@@ -945,7 +945,7 @@ public static class Parser
 
     public static string Normalize(string name)
     {
-        return NormalizeRegex.Replace(name, string.Empty).ToLower();
+        return NormalizeRegex.Replace(name, string.Empty).Trim().ToLower();
     }
 
     /// <summary>