Test that source/javadoc artifacts are optional when using maven scheme with ivy repository
REVIEW-4523: Test fixture tidy up
REVIEW-4523: Don't use internal types in fixture that tests artifact query api
REVIEW-4523: Verify message for artifact resolution failure with unknown component
REVIEW-4537: Expose failure to determine set of artifacts as an UnresolvedSoftwareComponent

- Removed SoftwareArtifactSet
REVIEW-4537: Removed unused type parameter
REVIEW-4413: Verify artifact failures
REVIEW-4436: Test that we check for new source/javadoc artifacts when the module descriptor changes

- Test for maven snapshot
- Test for ivy changing modules