Add optional Query Info dialog (grids)

[vanstyn]

It would be nice to be able to turn on access to view and debug details of the current query for DataStores/grids. For grids, if this feature is active, the 'query time' display in the toolbar would become a link to open a dialog to display info about the query.

This dialog would make an Ajax call to a new action which would need to be added to DbicLink2 which would simulate a read and build the ResultSet(s), but instead of executing it would return diagnostic information including:

• as_sql dump for both main query and total count query
• Dump of $Rs->{attrs} for both
• Any other useful info I haven't thought of yet