Accept installer-types and installer-paths specified in the composer.json of the included packages

[jcnventura]

I'd like to have an option to turn on some sort of 'recursive mode', where the definitions for installer-paths and installer-types can be inherited from the composer.json files of the included packages.

This option would be off by default to maintain current functionality, but when enabled it would allow us to specify types such as npm-assets in the composer.json of the package that requires it, instead of having to provide instructions to add these lines to composer.json when requiring a given package.