README: Updated README.

Removed module references which are transferred to syslog-ng upstream,
and updated syslog-ng version requirement.
kafka: Use correct stats header file
configure: turn on silent rules if it is possible

Signed-off-by: Juhász Viktor <viktor.juhasz@balabit.com>
ZMQ: Added zmq source, destination and transport
ZMQ: Make useage of zmq automatic

 * It means if user didn't set --enable-zmq,
   but zmq is installed it will compile with zmq
ZMQ: removed unused zmq_install.sh

 * It doesn't belong to incubator. It needed for travis only.
ZMQ: fixed zmq libs and cflags
ZMQ: Fixed segfault during reader deinit
ZMQ: Followed up 3.6 related changes

 * stats and other headers location
 * transport init_instance instead of init_method
 * GlobalConfig handling
 * LogThreadedDestination insert handling
ZMQ: added libzmq3-dev for travis
ZMQ: removed unused path option and added SCS_ZMQ
ZMQ: fixed source parsing
Merge pull request #87 from lmesz/zmq

ZMQ: Added zmq source, destination and transport
python: Try to log exceptions instead of segfaulting syslog-ng
python: Fixed segfault if non-UTF-8 string encountered in the message
Merge pull request #95 from talien/f/python-exception-handling

F/python exception handling
Initial version of grok support
grok: Add README
grok: Fixed grok grammar file.
grok: Added test stub