Merge branch 'stable-4.8' into stable-4.9

* stable-4.8:
  Fix NoSuchFileException during directory cleanup in RefDirectory
  Externalize warning message in RefDirectory.delete()
  Suppress warning for trying to delete non-empty directory

Change-Id: I5e6cc35f3673545e7ff857e6ed0bcd2c44e50316
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

diff --cc org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
Simple merge