The custom modules page now leads with plugin packages. Loading module
files with --load-module and MVT_CUSTOM_MODULES moves to a section on
developing a module locally.
A new "Writing a module" section shows a module which subclasses
IOSExtraction. It lists each base class, the command pair it serves and the
helpers it provides. "Depending on a built-in module" says to import a
built-in class from its family package.
"Importing from MVT" says what mvt.plugin exports and what importing from
it means. The custom commands page shows a Command subclass which lists its
own modules. The sysdiagnose and plugin configuration pages import from
mvt.plugin.
Donncha Ó Cearbhaill