Added lazy server and simple cache.

Added a lazy server implementation and added a basic file cache with an interface.

This was made because trying to fetch 2855 mails give me an **out of memory error**.
So now the search only populate a list of uid and the method **retrieveNextMessagesInLine()** retrieves the nexts ones. 

Also I implemented a basic cache interface and a file cache that saves the queries and fetched mails.
It improves the performance of the server because only goes for the ones that it doesn't have on cache.

And for last I create the method **closeImapStream()**. that simple close the imap connection.