images api v1.0 functional tests (tempest parity)

Depends on:
Change-Id: I5992df42cc3513aeedf3576b6884e357ac088622

 - some style changes
 - completed tempest test parity for this set of tests
 - rename image/ to images/
 - improve fixture

Change-Id: I04d39b9c1ef3902dbe36c0d1535a370f5fd5e57b