daemon: added signature verification of name

Verification is done in two ways, first it checks if the public-key
actually matches the registered name,
and second it uses the public-key to verify the signature.

These two checks are sufficient to guarantee that owner of the
registered name is the one who posted name data to the
blockchain nameserver.

Change-Id: If5cfd0eeb01b305f290b7a5e7d424688ccf8ccb1