Added and implemented a basic command-line parser.

This replaces the switch-case in HandleCommandLine and HandleCommandLinePostConfigLoad

TShockAPI/CLI/FlagSet.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace TShockAPI.CLI
+{
+	/// <summary>
+	/// Describes a set of flags that are responsible for one CL argument
+	/// </summary>
+	public class FlagSet : IEquatable<FlagSet>
+	{
+		private IEnumerable<string> _flags;
+
+		internal object callback;
+		internal Action continuation;
+
+		/// <summary>
+		/// Whether or not the set of flags represented by this FlagSet is followed by an argument
+		/// </summary>
+		public bool NoArgs { get; set; }
+
+		/// <summary>
+		/// Creates a new <see cref="FlagSet"/> with the given flags
+		/// </summary>
+		/// <param name="flags">Flags represented by this FlagSet</param>
+		public FlagSet(params string[] flags)
+		{
+			if (flags == null)
+			{
+				throw new ArgumentNullException(nameof(flags));
+			}
+
+			_flags = flags.Select(f => f.ToLowerInvariant());
+		}
+
+		/// <summary>
+		/// Creates a new <see cref="FlagSet"/> with the given flags and arguments option
+		/// </summary>
+		/// <param name="flags">Flags represented by this FlagSet</param>
+		/// <param name="noArgs">Whether or not the flags specified will be followed by an argument</param>
+		public FlagSet(string[] flags, bool noArgs) : this(flags)
+		{
+			NoArgs = noArgs;
+		}
+
+		/// <summary>
+		/// Determines whether or not this flag set contains the given flag
+		/// </summary>
+		/// <param name="flag"></param>
+		/// <returns></returns>
+		public bool Contains(string flag)
+		{
+			return _flags.Contains(flag);
+		}
+
+		/// <summary>
+		/// Determines whether or not this flag set is equatable to another
+		/// </summary>
+		/// <param name="other"></param>
+		/// <returns></returns>
+		public bool Equals(FlagSet other)
+		{
+			if (other == null)
+			{
+				return false;
+			}
+
+			return other._flags == _flags;
+		}
+	}
+}