+ * @brief Takes a list of public keys and updates them in the DB.
+ * @param keys The keys to update in the DB.
+ * @param blacklist A keyarray of fingerprints that shouldn't be added.
+ * @updateonly: Only update existing keys, don't add new ones.
+ * @param sendsync If we should send a keysync mail.
+ *
+ * Takes a list of keys and adds them to the database, merging them with
+ * the key in the database if it's already present there. The key list is
+ * update to contain the minimum set of updates required to get from what
+ * we had before to what we have now (ie the set of data that was added to
+ * the DB). Returns the number of entirely new keys added.