adding variable #conn_pool_name# to --filename-templates (export)

[daust]

For exporting database objects, we can define a naming scheme for the export, e.g.:

--filename-templates 
default:#schema#/#object_type_plural#/#object_name#.sql 
package:#schema#/packages/#object_name#.pks 
"package body:#schema#/packages/#object_name#.pkb"

We need another variable #conn_pool_name# to use the connection pool name instead of the connected database user. This is required when the connection pool name differs from the connection pool name.