Endpoint now pushes up faster formats if an unsupported format is
requested.

Unsupported formats will require transforming, and therefore parsing. If
we're parsing, we should pick a format we can parse most quickly.
Endpoint.query() now takes defer arg, to mimic previous behaviour.
archive task now uses new streaming API.
Fixed GraphListView (CannedQueryView before HTMLView in mro)
Moved undefer from CannedQueryView to StoreView.
Added functions for finding parsers/serializers by extension.