sig calculation and output follows pbp scheme. unittests, doc and

detached sigs still missing.

ChangeLog

@@ -12,17 +12,16 @@
 
 	Encrypted file format/scheme changed. Previously
 	I included the sender's key-id with the encrypted
-	cipher as a hash. Now the sender's public key will
-	be included directly. This way I don't have to reveal
-	key-ids (which is bad) and people can encrypt for
-	others without a full key exchange first.
+	cipher as a hash. So, encrypted message do no more
+	contain pk material.
+
+	Changed signature scheme completely. Binary signature
+	follow the pbp scheme: calculate blake2 hash of the
+	content, sign the hash, write out original content,
+	add "\nnacl-", add the signature, add the hash.
+	Armored signatures are calculated the same way but
+	output follows the pgp scheme instead.
 
-	Also I'm no more using the primary secret (or any
-	other secret in the vault) for encryption. Instead
-	every time a user encrypts a file, a new keypair
-	will be generated. That way the file can only be
-	decrypted by the recipient (which public key have
-	been used) and no one else, not even the sender.
 
 0.1.5   Fixed a segmentation fault when using pcp1 -t on a
 	public key. I added a double free() there by purpose