Core Sub-Module Support

[Nico Knoll]

Hey,

there are a lot of modules using submodules recently which is great in my opinion because it underlines the way Processwire works.

Examples are for example: Apeisa's Payment and Shipping modules, netcarver's new ProcessDiagnostic module and Adrian's ProcessMigrator.

All of them are using more or less different approaches - abstract classes, etc - and I'm not sure which is best. But I think a core support for submodules could be a nice addition.

One way to do it could be a "parent-module" setting in submodule's "module config" and a "getSubmodules" function in parent classes. Maybe you could add an abstract class like done with ConfigurableModule for this reason (e.g. ParentModule). 

Additionally apeisas way to use a abstract class would stay possible but wouldn't be necessary with this approach.

What do you think?

-- Nico