Until we correctly make MapLocation relation with mappables a polymorphic
one... we'll need to return the investment_id and proposal_id values.
Right now it was returning the MapLocation ID, and the JS was making a
call searching for an Investment with the MapLocation ID... sometimes
finding a record with same ID but totally NOT the one associated to the
MapLocation.
When editing the map of a proposal or investment(the mappable) the
updated_at attribute of the mappable was not been updated and so the
map still displayed the old location after updating it
