Update Memory

[Javier Pérez Pacheco]

In order to fix some problems with the way to order the memory in the conversations, we need to change the way to store the memory

1. We have to remove the timeStamp and the approxTokens in the Memory. The memory could be something like this:

data class Memory(val conversationId: ConversationId, val content: Message, val index: Int)

2. The index is an ordered number that the conversation is incrementally added to.