Refactoring into components

Refactoring this repository into repositories:

• args-model (core data structures)
• args-application (implementations of the retrieval pipeline, imports args-model)
• args-api (interface of the server, imports args-model)
• args-server (the actual server, imports args-application, args-api)
• args-client-html (XSL and resources for the HTML client)

This repository (args-framework) should include all above repositories and provide the configuration file to run the server. It serves as the main entry point for documentation.