Allow default implementation for abstract target field

[igarashitm]

Right now Java field writer only supports concrete class which can be instantiated via no-arg constructor. See createObject() in this class:
https://github.com/atlasmap/atlasmap-runtime/blob/master/atlas-java-parent/atlas-java-module/src/main/java/io/atlasmap/java/module/DocumentJavaFieldWriter.java

One option is to feed a mapping between interface/abstract types and default impl classes from configuration or something.
java.util.List : java.util.ArrayList
java.util.Map : java.util.HashMap
...

And it also should be configurable from mapping file so that the user can define their own types.