Added 'getRankedDocuments(String queryID, int numberOfDos)'
removed 'getRankedDocuments()' since it's replaced by 'getRankedDocuments(String queryID, int numberOfDos)';
Also added 'getNumberOfDocuments()' to obatined number of doces retrived for query
added 'calcPercisionAt(String queryID, int at)'.
'calcAveragePercisionSocre(String queryID)' is now using the above method