Refactor system/member avatar code

PluralKit.Bot/CommandSystem/ContextArgumentsExt.cs

@@ -60,6 +60,9 @@ namespace PluralKit.Bot
             return potentialMatches.Any(potentialMatch => flags.Contains(potentialMatch));
         }
 
+        public static bool MatchClear(this Context ctx) =>
+            ctx.Match("clear", "remove", "reset") || ctx.MatchFlag("c", "clear");
+
         public static async Task<List<PKMember>> ParseMemberList(this Context ctx, SystemId? restrictToSystem)
         {
             var members = new List<PKMember>();

PluralKit.Bot/CommandSystem/ContextEntityArgumentsExt.cs

@@ -2,7 +2,6 @@
 
 using DSharpPlus;
 using DSharpPlus.Entities;
-using DSharpPlus.Exceptions;
 
 using PluralKit.Bot.Utils;
 using PluralKit.Core;