OPENDJ-1991 Code cleanup

* org.opends.server.types.BackupDirectory
** Autorefactor'ed file
** Reformat
** Moves some constants to static
** Use Collection interfaces instead of implementation as declarative type
** Inline some message local variables
*** getLatestBackup()
*** BackupDirectory(...)
**** factorize code
** Simplify code of last loop in readBackupDirectoryDescriptor(String)
** Extract some methods to improve code lisibilty

* org.opends.server.types.BackupInfo
** Consequence of the change done in BackupDirectory

* org.opends.guitools.controlpanel.ui.BackupListPanel
** Autorefactor'ed file
** Reformat
** Moves some constants to static
** Use List instead of ArrayList as declarative type
** Extracted methods:
*** updateUI(boolean, BackupTableModel)
*** performSuccessActions(Set<BackupInfo>, BackupTableModel)
*** performErrorActions(Throwable t, BackupTableModel model)
*** getBackupPath(ServerDescriptor desc)
**** Consequence of this extract in configurationChanged(ConfigurationChangeEvent)