Add support for multi-user decryption

* Add CLI support using the command "twrp decrypt <PASSWORD> [USER ID]"
* Add GUI support using the menu Advanced --> Decrypt User

Change-Id: Id2681bc2b1012a0571417f7a6e0b980b1b25c61c
(cherry picked from commit 5a79f67a1b1bd1bcadeca0a4896a871646652534)

orscmd/orscmd.cpp

@@ -45,7 +45,7 @@ void print_usage(void) {
 	printf("  wipe <partition name>\n");
 	printf("  sideload\n");
 	printf("  set <variable> [value]\n");
-	printf("  decrypt <password>\n");
+	printf("  decrypt <password> [USER ID]\n");
 	printf("  remountrw\n");
 	printf("  fixperms\n");
 	printf("  mount <path>\n");