* Added per-message size limit to send&receive

	* Added per-message size limit to send&receive
	* Added per-account amount limit to s&r
	* Added per-account retrieve last N feature
	* Added an unique id to each mail operation
	* Renamed id field of mail operation by operation type
	* Added ModestMailOperationState to provide progress information
	* Added a new parameter of type ModestMailOperationState to progress-changed signal
	* Added an internal object to mail operation to get the new messages after a refresh

pmo-trunk-r1972