PluginRequirements should not be fulfilled unless their PluginRequirements are fulfilled

[ikelos]

A PluginRequirement should verify that the required plugins can successfully be instantiated. As such we need to verify the subset of requirements that may be required (at the moment, only other plugin requirements and module requirements, possibly all version requirements). It needs a little bit of thought, as to what's actually needed (most requirements are inputs, that aren't necessarily required for exposed methods), but at the moment a dependency may be fulfilled with a non-functional plugin.