Added basic query support to Async (not in Sync yet)

Added "user-function" support to CommandSeq -- so you can have user-defined code that
is called after an async Apigee call, and that function can see the response data.

Also added an "insertBefore" option to CommandSeq -- so your user-defined code can
see the response from, e.g., a query and then insert more commands into the sequence,
but insert them before a "logout" command.