Improve web.xml for CMS and site

We can set the <display-name> and <description> with the same values as the name and description set in the POM. it would be better than the generic "Hippo ECM WAR package" and "Hippo Site Toolkit Container Web Application" which are used by default in all projects. Also maybe it is a good idea to define the webapp id.

A few other things:

• with servlet 2.5, the <context-param> must define the description first, then the param names and values.
• <exception-type>Exception</exception-type> must be <exception-type>java.lang.Exception</exception-type>
• <dispatcher>REQUEST</dispatcher> is to bwe used with INCLUDE or FORWARD (http://download.oracle.com/docs/cd/B32110_01/web.1013/b28959/filters.htm#BCFIEDGB)