dscquery output DSC_REPLICATE column by default

[gaow]

Currently this info is only available when users query it. We should make it default when number of replicates is greater than 1.

[gaow]

Okey with this patch eb34e7a now every query will report DSC replicates under column name DSC (one of the few reserved words I now abuse for replicate column names). The patch, albeit short, is non-trivial -- in fact the entire query part is not straightforward SQL at all, due in large part to our group mechanism, and any changes to the code would possibly break things. I pushed the changes anyways and close the ticket for now. It is very crucial at this point to have bigger test suite for dscrutils::dscquery.