Display error.

* src/dctc/java/com/dataiku/dctc/display/AbstractThreadedDisplay.java,
  src/dctc/java/com/dataiku/dctc/display/AbstractTransferRateDisplay.java: Here.
Correct the synchronization problem while the copy.

* src/dctc/java/com/dataiku/dctc/copy/CopyTaskRunnable.java: Cache the
  size of the input file. Add getInSize to access to this
  value. Delete size method.
* src/dctc/java/com/dataiku/dctc/display/AbstractTransferRateDisplay.java,
  src/dctc/java/com/dataiku/dctc/display/NCursesDisplay.java,
  src/dctc/java/com/dataiku/dctc/display/SimpleDisplay.java: Adjust.
* src/dctc/java/com/dataiku/dctc/file/FTPFile.java: delete unused
  synchronization.
Clarify exception message for ls and ftp.

* src/dctc/java/com/dataiku/dctc/command/Ls.java,
  src/dctc/java/com/dataiku/dctc/file/FTPFile.java: Here.