pkcs15: use 'direct' public key value

pkcs15: in pubkey-info data
 * introduced new 'direct' 'raw' and 'spki' members
 * removed 'encoded der data' member
 * in 'read-public-key' try firstly SPKI direct value

pkcs11:
'direct' data used when getting CKA_VALUE attribute of public key

pkcs15init:
 * initialize 'raw' and 'spki' direct public key value