ivy maven install should also install -javadoc.jar as well

Like sources, javadoc should be generated and published via maven.

This means that in IDE's like Eclipse use of the Avro APIs will have handy javadoc tooltips and auto-complete options will contain javadoc. Also, it is becoming the standard way to distribute javadoc alongside code and source.

I assume, this is done very similarly to AVRO-416.