GroupsummaryQuery: distinct columns/desiredColumns

I guess this needs some more investigation, desiredColumns are the
ones the user asked for ([alias => ]column), with column being once
again an alias in the "real" query. Alias resolution used to work
better long time ago, we should reflect on this.
DataView: remove duplicate case handling
Ido/EventHistoryQuery: obsolete raw_timestamp

This was never thought to be used in frontends. Frontend code ALWAYS
needs to work with unix timestamps, raw timestamps are used internally
(e.g. between View and Query) to achieve better search and sort
performance.