Feature/update

Hi Nicholas,

Thanks for your awesome work for the update implementation. I've also implemented it and added some improvements. This PR contains some cosmetic improvements. I don't know if you like all the modifications, but there's potential ;) 

1. Adding the version information to the header might confuse people. Users could think their actual version is the displayed version number. I've moved the version number to the update button. 
2. I've renamed the reload update button to Find Updates. I think that's better and it's inline with the Joomla core button.
3. Please see the commits for more info. 

If you'd like me to add this to more extensions of you then I'd love to do that. 

Kind regards,
Jurian Even