archive-dump. Preserve symbolic links

Hi all!

Here is a patch.
How to use:

1. Create a symbolic link inside your Drupal root directory.
2. Execute a command: drush ard --destination=/path/to/backups/test.tar.gz --preserve-symlinks
3. Check your test.tar.gz file. It must contain the symbolic link from first step.

Regards!

Forgot to set new status...

Could be useful in case where you have a large data directory which should not end up in regular dumps.

Absolutely true!

Also --preserve-symlinks feature will be useful for testing your features or .install files.

Imagine you are developing a module which doing some changes with the database during installation process. Sometimes it is very painful to debug it...

The best way to test it:

1. Put your module in some place like, ~/modules/my_module
2. Create symbolic link to this module inside sites/all/modules directory
3. Then backup your site with drush-archive --preserve-symlinks

Now you can relax and test your .install file or feature as much times as you want. All you need is to restore site with drush-restore command.