Disease occurrence weightings

- Add method to DataAcquisition Main that is executed weekly - by comparing against value in internal properties file
- Calculate the weighting of an occurrence as the average over all experts' reviews in DB (review response x expert's weighting), for all the occurrences with new reviews. (At present this sets the "validation weighting" - next story separates this field into "expert weighting" and "system weighting").
- Note that reordering of methods within ExpertService and DiseaseService has appeared as deletions and additions.