Reduce conflicts, and improve installation notification.

Reduce conflicts with other extensions by detecting rewritten order grid node. Also imporved installation experience with successfull installation notification on Magento versions that support the method.

Usability improvements.

Added some small usuability updates, mainly set a default status color to make it obvious that the extension has been installed. As per issue #2.

Also added a notification to the Admin bar to make it even more obvious that the extension has been installed aswell as poining the user to two handy locations and adding the documenation link as the "Read Details" of that admin notification.