BQ2BQ Replace load dispostion doesn't handle aggregations

[sravankorumilli]

Options

1. Add an extra option in Replace load dispostition to take input from users to replace a specific or range of partitions using literals / all , dstart, dend. Default is all : all represents splitting of query to multiple partitions from dstart to dend.
2. Use a new Load Disposition, to replace to a single destination partition which is window start