JImageHelper to handle base64 encoded streams

I found that with the use of base64-encoded data streams of image files it should be possible to integrate the creation of such streams and that JImageHelper is the best place to request it from. So i added two new methods - toBase64 and fromBase64. While the former method generates a ready to use base64-encoded data stream that can be used with an `<img/>` element's src-attribute as well as with CSS the latter takes such a stream and writes it into an image file.

The methods can be tested the following way:

```
// Array of different input types and input path scenarios to show the paths are properly handled
$files = [
   'http://www.example.com/images/powered_by.png',
   '/abs/path/to/joomla/images/powered_by.png',
   '//images/powered_by.png',
   '\\images\powered_by.png',
   'images\powered_by.png',
   '\\abs\\path\to\joomla\images\powered_by.png',

   'http://www.example.com/images/joomla_green.gif',
   '/abs/path/to/joomla/images/joomla_green.gif',
   '//images/joomla_green.gif',
   '\\images\joomla_green.gif',
   'images\joomla_green.gif',
   '\\abs\\path\to\joomla\images\joomla_green.gif',

   'http://www.example.com/images/joomla_logo_black.jpg',
   '/abs/path/to/joomla/images/joomla_logo_black.jpg',
   '//images/joomla_logo_black.jpg',
   '\\images\joomla_logo_black.jpg',
   'images\joomla_logo_black.jpg',
   '\\abs\\path\to\joomla\images\joomla_logo_black.jpg',

   'http://www.example.com/images/joomla_logo_black2.jpeg',
   '/abs/path/to/joomla/images/joomla_logo_black2.jpeg',
   '//images/joomla_logo_black2.jpeg',
   '\\images\joomla_logo_black2.jpeg',
   'images\joomla_logo_black2.jpeg',
   '\\abs\\path\to\joomla\images\joomla_logo_black2.jpeg'
];

// Iterate over the files array and output every image to your browser
foreach ($files as $f)
{
   echo '<img src="' . JImageHelper::toBase64($f) . '" border="0" alt="Image"/>';
}

$streams = [
   'powered_by.png'        => 'data:image/png;base64,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',
   'joomla_green.gif'      => 'data:image/gif;base64,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',
   'joomla_logo_black.jpg' => 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'
];

// Iterate over the streams array and create files to the /tmp folder.
foreach ($streams as $name => $stream)
{
   JImageHelper::fromBase64($stream, true, $name, '/tmp');
}
```
Please test and report back.
As stated, this is not my code. The method `generateThumbs` expects two arguments:
```
* ...
* @param   mixed    $thumbSizes      String or array of strings. Example: $thumbSizes = array('150x75','250x150');
* @param   integer  $creationMethod  1-3 resize $scaleMethod | 4 create croppping | 5 resize then crop
* ...
```
Our discussion refers to the first argument. The method evaluates the passed string explode to an array of 2 values. 
```
$size = explode('x', strtolower($thumbSize));
```
If this is not true, then this message is shown. Taking your translation suggests that the desired size was entered into a form. I doubt that this is the case. Rather the parameter is passed through a function call. So *received* is the proper term.