Change module folder naming convention to fit typeName instead of collectionName

[eric-burel]

Following discussion with @Neobii , using the plural collectionName is a source of complexity, discrepancies and even bugs.
Automatically computing the plural can give unexpected results (like "schema" > "schemata" instead of the more usual "schema") and even name clashes.

Instead, the typeName, singular should be preferred on many occasions. All the more that in the future we may have more and more GraphQL type not tied to a collection anyway.

This applies especially to directory names modules/movies > modules/movie.

We should take that into account during next updates, when we modify a package it's an occasion to also rename its directories.