Update dst key code to maintain key state

Update dst key code to maintain key state

Add a number of metadata variables (lifetime, ksk and zsk role).

For the roles we add a new type of metadata (booleans).

Add a function to write the state of the key to a separate file.

Only write out known metadata to private file.  With the
introduction of the numeric metadata "Lifetime", adjust the write
private key file functionality to only write out metadata it knows
about.