Add the option for a plugin to have multiple commands.

[julxyz]

Problem

A plugin can only have one command at the moment.

Proposed Solution

Commands should be defined in the plugin's manifest like this:

def manifest():
    manifest = {
    "commands": {
        "command name one":  {
            "function": "function_name",
            "permreqs": ["manage_messages"],
            "aliases": ["func", "fart"]
            },
        "command name one":  {
            "function": "function name",
            "permreqs": [],
            "aliases": ["förk", "spoon"]
            }
        },
    "eventhooks": []
    }