check all device ownership edge cases

[idokleinman]

From @idokleinman on February 24, 2015 1:36

(1) device not claimed c=0 — device should also not be in list from API => mobile app assumes user is claiming and sets device claimCode + check its claimed at last stage
(2) device claimed c=1 and already in list from API => mobile app does not ask user about taking ownership because device already belongs to this user, does NOT set claimCode to device (no need) but does check ownership in last setup step
(3) device claimed c=1 and NOT in the list from the API => mobile app asks whether user would like to take ownership. YES: set claimCode and check ownership in last step, NO: doesn't set claimCode, doesn't check ownership in last step

relevant to #49

Copied from original issue: spark/mobile-sdk-ios#57