Refs #0001   Implementing request for public key name

Also in this commit:
- command line tool (ndn-pubkey-name) to retrieve stored public key name

Change-Id: I28b903f41d6174dfc07edbeb23dadac8e02b1375
Refs #0001   New helper script ndn-install-pubcert to check and install .pubcert file into the right location

Change-Id: Idcf066f292ebf898d59fb70d178bf60aa142c014
Refs #0001   Two more helper scripts: to extract public key and to automate application key signing

ndn-sign-key is a simplified version of the original script from
http://github.com/named-data/ndn-testbed-key-suite repository, which
combines usage of .pubcert and published keys to infer most of the
signing parameters.

Change-Id: I86607f1d581d61eaf773296af46ed8243f84d7bb