remove unused methods on DependencyAnalyzer and DependencySet
    
    The CLI stays the same, although this is an API break for anybody who
    was calling these methods through the Python API directly.
    
    Deleting them now gives us less to document and commit to, and less to
    port over to libsolv.
    
    Change-Id: I4cf62cb561022caf468bec424c57870ec6f12129