[jose] x5c, x5u, x5t don't apply to all key types

[Brian Campbell <[e-mail]>]

Section 3 of JWK [1] defines "members that are common to all key types" and
includes among those members x5c, x5u and x5t. However, the x5X parameters
are relevant only for half the key types defined in JWA - they don't really
make sense for "oct" [2] or "PBKDF2" [3].

Not sure the best way to address this but it seems kind of awkward as it
is. Maybe move them into the EC and RSA type definitions (or something
common to both) or somehow add some qualifying text saying that they can
only be used with key types utilizing public keys?

As I was looking up the URLs below I noticed that the section alignment in
section 5 of JWA is a little off. I think 5.3.3 and 5.3.4 should probably
be 5.4 and 5.5 respectively. Right now they line up as though they were
part of the RSA key type.

[1] http://tools.ietf.org/html/draft-ietf-jose-json-web-key-13#section-3
[2]
http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-5.3.3
[3]
http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-5.3.4