Revision 924176

Added ZeroConf support to most of the network-based appenders and receivers.

To enable ZeroConf advertising of an appender or receiver, a user can now:
 - add jmdns jar to their classpath 
 - set the 'advertiseViaMulticastDNS' param to 'true'

Also added support for discovery of appenders in Chainsaw (Chainsaw will automatically configure a matching receiver when connected).
Supported appenders:
    SocketAppender
    SocketHubAppender (ZeroConfSocketHubAppender is still functional)
    UDPAppender
    MulticastAppender
Supported receivers:
    SocketReceiver
    SocketHubReceiver (also receives events from ZeroConfSocketHubAppender)
    XMLSocketReceiver (can receive events sent over TCP by other logging frameworks)
    UDPReceiver
    MulticastReceiver

Implementation details:
 - removed Zeroconf4log4j class, jmdns access is now through the ZeroConfSupport class (class provides support of JmDNS and ServiceInfo creation via reflection, and supports both jmdns 1.0 and jmdns 3.1 apis)
 - ZeroConfSupport class is now used by ZeroConfSocketHubAppender, Chainsaw and all appenders & receivers that can advertise their configuration via ZeroConf
 - added new 'advertiseViaMulticastDNS' param to the appenders and receivers that support ZeroConf
 - updated the ZeroConf site documentation
 - updated release notes
 - updated the ZeroConfPlugin html file
 - tested appenders with 1.0 and 3.1 jmdns jars
 - updated log4j references in poms to log4j 1.2.16-snapshot where necessary 

For those wanting to add ZeroConf support to third-party appenders and have Chainsaw discover the appenders, the service info naming convention is described here: https://issues.apache.org/bugzilla/show_bug.cgi?id=48907