1. A system comprising: a processor; a memory; one or more designers and a visualizer, the one or more designers and the visualizer configured to visually formulate application package designs that customize the appearance and layout of corresponding application packages; a package generator for generating application packages from application package designs, generated application packages being in a format expected by product deployment software; and one or more computer readable storage devices having stored thereon computer executable instructions that, when executed by the processor, cause the system to: customize an application package design, including: present the structure of an application package through an arrangement of user-interface elements in a view of the visualizer, the user-interface elements corresponding to application package element references, the application package element references referencing application package elements; receive user input within the visualizer view; in response to the user input: visually alter one or more user-interface elements in the arrangement of user-interface elements; and alter the structure of the application package by the one or more designers altering application package element references corresponding the visually altered one or more user-interface elements; and generate a customized application package from the customized application design, generation of the customized application package including: create an application package element manifest by traversing the altered structure of application package in accordance with the application package element references to identify application package elements that are to be included in the customized application package; transform the application package element manifest into one or more manifest files in a format that is compatible with a packaging schema for the product deployment software by mapping between types and properties in an object model and elements and attributes in the packaging schema; preview the customized application package on disk by creating, from the one or more manifest files, a directory hierarchy comprising the identified application package elements and placing the identified application package elements in locations relative to the directory hierarchy on at least one server computer of the plurality of server computers; and use the directory hierarchy to bundle the identified application package elements into one file for deploying the collaborative server application across the plurality of server computers, the one file in a format expected by the product deployment software.