Validate command should process all recipes

[scymtym]

Is your feature request related to a problem? Please describe.

When I run

build-generator validate PATH/recipes/

the generator does not report the following problems:

• Errors in project recipes that are not included in any distribution

• Errors in project versions that are not included in any distribution

Describe the solution you'd like

The validate command should process all recipes, including all versions of projects and check them to the extent possible. Things like project versions using the pattern: form may not be completely checkable, but at least syntactic well-formedness (currently checked in included project recipes) and schema conformance (currently checked in included projects and project versions) should be checked.