Displaying a templated response on block instead of redirecting.

It supports all the format tokens that the LogFormat directive supports,
plus %mn for displaying the virus name.as identified by ClamAV.
Updated all documentation to mention new behaviour in the absence of the redirection option.
Merge pull request #13 from nathan-hoad/icap-response-instead-of-redirection

Provide the ability to display a configurable template instead of redirection