pagination support in the update function
pagination support in the update function

* handle GetNextPage | GetPrevPage
* handle OnNextPageResult | OnPrevPageResult
  the model is only updated if the channelName and first/last element
  of messages matches the one when the request was sent (to avoid
  delayed/duplicated responses)

* update_seq -> last_seq as changed in the model
* results -> rows as changed in the model

gdamjan/irclog-couchapp,gdamjan/irclog-couchapp