More Java viewer clipboard handler fixes

* Override TransferHandler.exportToClipboard method to ensure that
  serverCutText updates get sent to the system clipboard.  This
  wasn't always happening when relying on the super class' paste()
  method alone.
* Removed some unnecessary setText() statements and one check for
  whether sending client cut text is enabled.
Merge pull request #75 from bphinz/java

More Java viewer clipboard handler fixes