Added subcommands

[PillageDev]

This PR adds the ability to have a command be registered as a subcommand and still function normally.

To create a subcommand, first you have to register a subcommand category off of the JDAIntegration object.

JDAIntegration commandIntegration = new JDAIntegration(jda);
commandIntegration.addSubCommandGroup(new CommandDataImpl("test", "test"));

To create a subcommand under that category, you have to edit the annotation on the method like the following:

@HandleSlash(name = "exampleCommand", desc = "Description", global = true, subCommand = true, parentGroup = "test")

If there is no subcommand group registered under a name "test" or any other command marked with that parent group name, then the program will throw a NoSuchElementException

If there is a better way to do any of this please let me know!

[PillageDev]

I also fixed a small issue when you register a guild command then it would still say that there was an error registering it. That was caused by an issue with the if statement
Old:

if (guild != null) {
    guild.upsertCommand(data).queue();
} if (KCommando.verbose) {
    Kogger.warn("Guild not found for Slash Command named as " + name);
}

New:

if (guild != null) {
    guild.upsertCommand(commandData).queue();
    if (KCommando.verbose) {
        Kogger.info("The SlashCommand that named as '" + name + "' is upserted as a guild command for guild '" + guildId + 
        "'");
    }
} else { // Guild is null; not found
    if (KCommando.verbose) {
        Kogger.warn("Guild not found for Slash Command named as " + name);
    }
}