Improve groupby webservices

[pfurio]

GroupBy webservices were returning the names of the elements that fell into each different group. However, it would be interesting not only that, but also having the possibility to just count the number of entries falling into every group. To do so, we would just add a new boolean field count in the groupby webservices to have that possibility. On the other hand, we should also add a new limit field to limit the number of entries that can returned by the groupby operation.

The groupby webservice should be also added to Family and ClinicalAnalysis.