data: Implementing Data::getFullName() method to get Data packet name with implicit digest

Note that getFullName() method will throw a Data::Error if Data packet
does not have wire encoding, i.e., it has not been constructed from wire
and is not yet signed.

Change-Id: I7a9b8a6c9e4c6eced9bc907bfc81adb5d4f0e4b3
Refs: #1298
security: Removing unused SecPublicInfoMemory and SecTpmMemory

These two classes were meant for testing purpuses only, are no longer
used anywhere in ndn-cxx, and are not known to be used by any
applications.

Change-Id: I9b6c68bdf23419b7a274f63a64711fa843c2502c
security+tools: Allow user to explicitly specify the cert name prefix before 'KEY' component in ndnsec-certgen

Change-Id: I71e137e89b5ab0cd5db7001b39ff76c22a448bd2
Refs: #1659