Add generic unlock key setting and removal.

* Replace {Set|Remove}MasterKey() by generic {Set|Remove}UnlockKey()
  that works on a keyring.
* Implement {Set|Remove}MasterUnlockKey() on top of that.
* Rename the commands and constants accrodingly.
* Implement setting and removing keyring unlock keys.

headers/os/app/KeyStore.h

@@ -57,10 +57,14 @@ public:
 			status_t			GetNextKeyring(uint32& cookie,
 									BString& keyring);
 
-			// Master key
+			status_t			SetUnlockKey(const char* keyring,
+									const BKey& key);
+			status_t			RemoveUnlockKey(const char* keyring);
 
-			status_t			SetMasterKey(const BKey& key);
-			status_t			RemoveMasterKey();
+			// Master keyring
+
+			status_t			SetMasterUnlockKey(const BKey& key);
+			status_t			RemoveMasterUnlockKey();
 
 			status_t			AddKeyringToMaster(const char* keyring);
 			status_t			RemoveKeyringFromMaster(const char* keyring);

headers/private/app/KeyStoreDefs.h

@@ -30,8 +30,8 @@ enum {
 	KEY_STORE_ADD_KEYRING					= 'KaKR',
 	KEY_STORE_REMOVE_KEYRING				= 'KrKR',
 	KEY_STORE_GET_NEXT_KEYRING				= 'KnKR',
-	KEY_STORE_SET_MASTER_KEY				= 'KsMK',
-	KEY_STORE_REMOVE_MASTER_KEY				= 'KrMK',
+	KEY_STORE_SET_UNLOCK_KEY				= 'KsuK',
+	KEY_STORE_REMOVE_UNLOCK_KEY				= 'KruK',
 	KEY_STORE_ADD_KEYRING_TO_MASTER			= 'KarM',
 	KEY_STORE_REMOVE_KEYRING_FROM_MASTER	= 'KrrM',
 	KEY_STORE_GET_NEXT_MASTER_KEYRING		= 'KnrM',