Handle autoloading of extension classes

[martinkrcho]

Let's discuss autoloading of classes in the extensions. I can see 2 options here.

1. We can have a composer based autoloading in each extension.
2. We can provide a hook in the main plugin to allow an extension to provide a namespace + directory path or some other parameters for an autoloader mechanism in the main plugin.

[DannyWPWS]

@martinkrcho do you mean the way we load the custom alerts/senors found in extensions or the way we include the core files? Also, forgive my ignorance but what would doing the above give us? Or is this something that could help in the future with more perhaps more complex extensions which we may produce?