temp: disabling key fetching in get

Change-Id: I6dd416f46bfdf0c897b90e54c1ab45efc8e4493b
(Temporarily) deprecating get method, changing callback API for expressInterestSimple

Change-Id: Ib34c1f894fd9525974edba99a6eec4a88b9a9c50
Deprecating closure-based interest expression (making it "private")

Change-Id: I1a7adb67de66b4aff38a54b2f8a9e18aa5535f65