"Add share" tool #97
Description
In V1, users could request that a "share" column was added. The indicators specification figured out (hidden from the user) which 'total' should be used for the calculation.
We should provide a tool in V2 which facilitates this. The user should be able to specify which indicator they want to use to be 'total' so this would be just a convenience feature to join that data and create a column as share.