List modules in machine-readable output

List of modules are read by turris/foris-controller/foris-controller-diagnostics-module> from help message. It parses this human-readable help message, which is really fragile (and depends on every whitespace etc.)

We should add an option to list modules with machine-readable output and also, possibly, to display help message for every module separately.

Listing modules should also include a simple test for module file names (e.g. no newlines, prepended number in given format, ...).