*) starting implementation of Content-MD5 header

   which should help to detect transfer errors on yacy to yacy
   communication
   - not finished yet
*) removing unneeded functions (e.g. respondHeader) because newly
   introduced functions in class httpd.java
*) httpdFileHandler.java now always sends back a proxy error message
   as body of a response with an error code
*) adding support of gzip content encoding 

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@244 6c8d7289-2bf4-0310-a012-ef5d649a1542