Changes for 3.1.0beta0.

Changes for 3.1.0beta0.

* Added new script BackupPC_archiveStart that allows command-line
  starting of archives.  Based on script written by Sergey Kovzik,
  which in turn was based on an earlier version by Holger Parplies.

* Added check to BackupPC at startup that $TopDir can support
  hardlinks. Also added check to BackupPC_dump that a hardlink
  below $TopDir/pc/HOST can be made to below $TopDir/cpool.
  Also added the need for a hard-link capable file system to
  the documentation.  Suggested by Nils Breunese.

* Made the default charset for BackupPC_zipCreate cp1252, which
  appears to work correctly with WinZip.  Unfortunately there is
  no clear standard for charset encoding in zip files.

* Added support so that pre-3.0 backups with non-utf8 charsets
  can be viewed and restored correctly.  A new config variable
  $Conf{ClientCharsetLegacy} specifies the charset used to
  encode file names in legacy backups.  This is only relevant
  if you are trying to view or restore a backup made with
  BackupPC 2.x and some of the file names have non-ascii
  characters.

* Added setting of the environment variable BPC_REQUSER to
  the requesting user name in BackupPC prior to fork(), so
  each child process inherits the value.  Submitted by
  Holger Parplies.

* Fixed bug in rsync incrementals that happens on particular
  file names when a file being backed up fails in both rsync
  phases.  Reported by Dan Smisko.

* Removed ConfDir from config editor (since it is hardcoded in
  lib/BackupPC/Lib.pm).  Also made TopDir and LogDir only visible
  if useFHS (for non-FHS they are hardcoded in lib/BackupPC/Lib.pm).