Bug: should not assume preferred list name is 'dev'

The code at

https://github.com/apache/incubator-ponymail/blob/master/site/js/ponymail.js#L4008

assumes that the preferred list name is 'dev'. This name should not be hard-coded as it depends on the installation.

Instead it should be a configuration item; better yet the config should have a default but allow overrides for individual domains within the installation.

Start at site/js/ponymail.js around line 4008 and trace how configuration is loaded. Done means the preferred list name is no longer hard-coded, has a default, and supports overrides for individual installation domains.

Written by the indexing model from the issue text.