Provide Upload tab + viewlet as an alternative to the portlet

Hi,

we often have the use-case that we'd like to provide quick-uploading functionality without the need for adding a portlet. (E.g. because the site design does not allow enough space)

This proof-of-concept pull request provides a simple alternative: An "Upload" tab, that will open the quick-upload box inside a viewlet below the Title. The original implementation came from my colleague @cillianderoiste

The Upload tab is displayed on all folderish items where the current user is allowed to add content:

![Screen Shot 2013-03-21 at 10 55 21 ](https://f.cloud.github.com/assets/642660/285094/b93de770-920d-11e2-9bb7-cc0880298693.png)


On click, the previously hidden viewlet opens. It behaves in the same way as the portlet (with default settings):

![Screen Shot 2013-03-21 at 10 55 56 ](https://f.cloud.github.com/assets/642660/285098/c8eb56a8-920d-11e2-846e-b0072eec04a1.png)

Limitations:

* Unlike the portlet, the viewlet does not hold any configuration. That means only the default settings (Content types from registry, Media = all) are possible
* Wherever the portlet is present, the Upload viewlet will not be displayed

An idea for improvement might be to add an option to the `@@quickupload-controlpanel` that turns displaying the "Upload" tab on and off - that way it would be less intrusive. But before I continue in that direction, I would like to get the package maintainers' general opinion about this feature.