Bug 1512 - generated builder java file for a leaf containing a union

Bug 1512 - generated builder java file for a leaf containing a union

- added clarification for location of builder class for union types
  into javadoc
- remove redundant check in YangTempla.writeRpcInput() and
  YangTemplate.writeRpcOutput() methods
- added return type for GeneratorImpl.printAugmentedNode() method
  (problem to infer return type in recursivecalled method)
- added local set of typedefinitions into
  GeneratorImpl.printSchemaNodeInfo() to to remove error in geterated java
  file

Change-Id: If4ad960a998254868a0347bb836c79aac7dd19d8
Signed-off-by: Ladislav Borak <lborak@cisco.com>