Support count(distinct field_name) with group by

When verifying SEARCH-900 and testing count(distinct) the following error was produced: 

java.sql.SQLException: java.sql.SQLException: java.io.IOException: 04110039 Unable to execute the query, error caused by: null

An example query: 

select count(distinct cm_name) as `Expense Name`, finance_amount, finance_location, finance_title
from alfresco
group by finance_amount, finance_location, finance_title

This query is a valid SQL query that should work and should get you the number of distinct 'cm_name' values within each group.

normal count(cm_name) within a group, will count how many rows in that group have a value and the count distinct(cm_name) within a group, will count the different values available in the rows group. 

Acceptance criteria:

• It should be possible to use "count(distinct field)" with "group by"