Advanced guide to managing your own application commands

[Th3-M4jor]

Guide for how you might manage your own Application Commands.

I chose to go with Ecto/EctoSQL in this example because that's more likely to be something readers are already to be familiar with as opposed to :mnesia or :dets.

And if they want to instead use either, its not too tough to switch to it on their own.

[Th3-M4jor]

A guide that's more or less based on what I do in my bot is ready.

When reviewing be as nit-picky as you want to be with this, if this might replace Nosedrum I want it to be as good as we can make it be.

Also, please squash merge the PR when/if its ready to merge

[jchristgit]

I'm a bit confused why people should implement their own manager in the first place - doesn't this reproduce what nosedrum does? https://github.com/jchristgit/nosedrum/blob/master/lib/nosedrum/storage/dispatcher.ex#L1

[jchristgit]

If you don't mind I would like to park this one for a while. I feel like storing the commands in a database is a bit too complicated for what we need. And I feel like the remaining behaviors should really be covered by nostrum itself with some simple application command behaviour.