Refactoring to add select_qry S3 generic.
Plus lots of other cleanup and simplification
Restrict compound to union all
Eliminate from function
Consistent name for lahman src in examples
Update compound with api changes
Separate simple fetch/exec sql functions.
Reinstate show and explain options
Don't try and explain modifying queries
Fixes for grouped_sqlite
Add same_src generic
Document join and add auto_index support