Allow setting IgnoreExtraArgs on an individual basis (#998)

* Allow setting IgnoreExtraArgs on an individual basis

* Remove passing in the flag as a separate parameter

* VS plz

* Push the RunMode setting out to its own attribute, because fox wants consistency.

Bonus: Removes the need for that godawful 'RunMode.Default'.

* Revert previous commit

* Fox doesn't like module-wide switches 😒

src/Discord.Net.Commands/Attributes/CommandAttribute.cs

@@ -7,6 +7,7 @@ namespace Discord.Commands
     {
         public string Text { get; }
         public RunMode RunMode { get; set; } = RunMode.Default;
+        public bool? IgnoreExtraArgs { get; set; }
 
         public CommandAttribute()
         {