[FEATURE] Apply filters to reply_to_message

[Bibo-Joshi]

This idea came up in the user group (here).
In some edge cases it might be useful to apply filters to the reply_to_message attribute of a message. Than can be achieved by something like

class ReplyToMessageFilter:
    def __init__(self, filter):
        self.f = filter

    def filter(self, message):
        if message.reply_to_message:
            return self.filter(message.reply_to_message)
        return False

That's basically already it, but it would need proper documentation and some testing