#2 Add possibility to force transformation to always happen

[František Řezáč]

Currently if the underlying filter chain returns response whith http 3xx (with no content), the transformation will not take place. The problem is that although the requested file itself doesn't change, other documents obtained through xpath document() function may be changed. This should be solved by deleting some http caching directives from original request before handling it over to the filter chain. It should be possible to force this behavior via servlet setting in web.xml.