Displaying the checkout icon when necessary

https://github.com/joomla-projects/com_localise/issues/208
To test use 2 browsers and edit a package, a translation or a language.
before patch = errors
after patch: the icon displays, example below for packages

![screen shot 2014-08-30 at 19 35 35](https://cloud.githubusercontent.com/assets/869724/4099726/25b96a5c-306c-11e4-8f4e-b55ccebf0ae3.png)


IMPORTANT: this is incomplete!
Instead of redirecting to the manager when someone clicks on the link of a checkedout item, it opens the edit page and as the close does not work, the only way for the user is to get back in browser.