Use config object for ve.ui.PagedDialog.addPage optional args

Objectives;

* Cleanup the addPage API
* Add optional index param to addPage method

Changes:

ve.ui.MWMetaDialog.js, ve.ui.MWTemplateDialog.js
* Update uses of addPage

ve.ui.PagedDialog.js
* Bundle existing optional arguments into object
* Add index option for inserting a specific index

Change-Id: Idcef4d0a52fb817c7d888990920b2c12224a3392