Pass a list of files to be displayed to the Gallery and Slideshow.

This is just an idea I've been playing with...

I've altered both the filemanager's gallery and slideshow so that you can pass either a `|` delimited string or an array that lists paths to images to be displayed.  That way, paths to images could be held in a database, for example.

As an example.  In the handler and passed to the view as part of the array argument to `render` :-
```php
$myfiles = 'homepage/photo1.jpg|homepage/photo2.jpg';
```
or
```php
$myfiles = array('homepage/photo1.jpg','homepage/photo2.jpg');
```
In the view:-
```
{! filemanager/slideshow?files=[myfiles|none]&name=homepage !}
```
`name` is the suffix to the slideshow's CSS ID tag which was extracted from the path in the original usage.

It's a similar scenario with the gallery, except that `name` is not used.