Backport : Generic External Web Application Framework Integration Support

Since HST-2 supports sitemap item handlers which can process the filter chain just after HstFilter (HSTTWO-2463), most Servlet Web Application Framework (such as Spring MVC, Cocoon, Wicket, etc) applications can possibly take advantage of HST-2 host/site/content mapping, session pool, html/link rewriting, tag libraries, etc. like normal HST-2 web applications.

In a nutshell:

• Expose FilterChain through the ValveContext
• Integrate ContentBeansResolvingValve into the HST
• Intergrate FilterChainInvokingValve in the HST and have it fetch the FilterChain from the valveContext (only in 'delegateToFilterChainPipeline')
• Create a new standard HST pipeline 'delegateToFilterChainPipeline'
• So, for example, we can define any sitemap item with the 'delegateToFilterChainPipeline'.