added exclude option to sync commands

Added an exclude argument to Rex::Commands::Sync::sync_up & sync_down. Should be mostly inline with the exclude argument in the Rsync.pm module.

Usage:
```perl
desc 'Sync test';
task 'sync', sub {
	use Rex::Commands::Sync;

	sync_up '.', '/tmp/test',
	exclude => ['log/*', 'init.d/', '*.conf'];
};
```