Allow Lua to supply date-formats.

  Date formats are necessary for parsing date: headers
 because dates are nasty.

  This fixes #67
  Updated the sample configuration file to avoid the
 demo-settings I've committed.

  e.g. remove the colour settings and the "ignored_folders".
  Exclude URLS from the // comment-testing.
  Use the global $tmp variable.

  We now don't use /tmp explicitly.  Instead we use
 $TMPDIR, or $TMP, then /tmp if neither is set.
  Use our tmp variable for message-filtering.

  This means we use $TMPDIR, $TMP, then /tmp if neither is set.
  Further bound the selection of folders/messages.

  This is an attempt to resolve #68.
Show all lines (email body) for which there is a place on the screen. #70
  Only reset the message when changing the index-limit.

  Also log variable settings.
  New function: has_flag()

  This is now used for adding flags, to avoid repeats.

  This is part of #71.
  Updated is_new().

  This correctly regards a message as new/unread if there is
 either:

  * A "N" flag.
  * A missing "S" flag.

  This updates #71
  Correctly handle new mails in index-view.

  Previously we looked for the flag "N", rather than calling
 `CMessage::is_new()`.

  This updates #71.
  Correctly determine the number of read/total messages.

  This updates issue #71.

  Unfortunately by keeping allocating and freeing CMessage objects
 for every file in the current maildir we are *horrifically slow*.

  We absolutely must cache things.  Suggest we add a general
 purpose caching class and then cache based upon the mtime of the
 maildir path.
  Use a regexp in the maildir-limit, just to prove a point.
  Remove the truncation of flags.

  This updates #71
  Avoid showing "." and ".." directories.

  This fixes #73
Don't iterate over files while looking for Maildirs
Merge pull request #74 from trou/master

Don't iterate over files while looking for Maildirs.
fix style : use spaces instead of tabs
  Use spaces, not tabs:  Caught by "make style".
  Removed CMaildir::countFiles().

  This function is obsolete.