Implement handling of complex modules (modules as a directory)

[ldelelis]

This would help decoupling certain logic from the kernel's code, while keeping module files uncluttered. See for example: server_stats module

[ldelelis]

Apparently, this is already possible, due to how module specification works in Javascript. All that's needed is that the module's directory contains an importable index.ts file. Should we document this somehow?

[ldelelis]

Documentation to be implemented by #64