Adjusted categories to include guildproperties and allow specifying position when creating channel categories

src/Discord.Net.Core/Entities/Guilds/IGuild.cs

@@ -474,12 +474,13 @@ namespace Discord
         ///     Creates a new channel category in this guild.
         /// </summary>
         /// <param name="name">The new name for the category.</param>
+        /// <param name="func">The delegate containing the properties to be applied to the channel upon its creation.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous creation operation. The task result contains the newly created
         ///     category channel.
         /// </returns>
-        Task<ICategoryChannel> CreateCategoryAsync(string name, RequestOptions options = null);
+        Task<ICategoryChannel> CreateCategoryAsync(string name, Action<GuildChannelProperties> func = null, RequestOptions options = null);
 
         /// <summary>
         ///     Gets a collection of all the voice regions this guild can access.

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -189,11 +189,18 @@ namespace Discord.Rest
         }
         /// <exception cref="ArgumentNullException"><paramref name="name"/> is <c>null</c>.</exception>
         public static async Task<RestCategoryChannel> CreateCategoryChannelAsync(IGuild guild, BaseDiscordClient client,
-            string name, RequestOptions options)
+            string name, RequestOptions options, Action<GuildChannelProperties> func = null)
         {
             if (name == null) throw new ArgumentNullException(paramName: nameof(name));
 
-            var args = new CreateGuildChannelParams(name, ChannelType.Category);
+            var props = new GuildChannelProperties();
+            func?.Invoke(props);
+
+            var args = new CreateGuildChannelParams(name, ChannelType.Category)
+            {
+                Position = props.Position
+            };
+
             var model = await client.ApiClient.CreateGuildChannelAsync(guild.Id, args, options).ConfigureAwait(false);
             return RestCategoryChannel.Create(client, guild, model);
         }