?column__in=value1,value2,value3 filter

[simonw]

Support for the SQL where column in (...) construct, inspired by the new design for facet configuration in #427

?column__in=value1,value2,value3 will map to where column in ("value1", "value2", "value3")

If comma separation won't work (because the values themselves contain commas) you can do this instead:

?column__in=["value1","value2","value3,with-comma"]

See also #288