In the overviews-specialized dataview classes the sql-generating
functions had an unneeded parameter filters.
In some cases, since this parameter was not being paaased from
the base dataviews class it was masking the override parameter.
Now QueryRewriter is used in dataview objects they can decide
whether overviews are applicable, have the oportunity to
adapt queries for overviews, etc.
This is done by having overviews-related behaviour in models/dataview/overviews
and falling back to the regular models/dataview.
Javier Goizueta