Reverse loop over messages to find quoted message. Improves performance as quoted messages will be near the current message (end of the messages iterator).

[nielsderdaele]

Opening a large chat (250k+ messages) takes a long time. One of reasons for this is the loop which tries to find a quoted message. This loop starts from the beginning of the messages and loops to the end. Almost always one will quote a recent message (near the end of the messages vector). I changed findMessageById method to findMessageByIdReverse so it runs from the end of the vector to the front. This greatly improves performance as the quoted messages is often found in a couple of iterations.