Manage the registered Studio package

We sometimes need to work on the registered Studio packages only or specifically, versus all the Studio Marketplace Packages the user has access to.

• "Registered Studio packages" = the Studio Marketplace Packages related to the Studio project which the server is registered with.
• "all the Studio Marketplace Packages the user has access to" : it is now possible to install other Studio packages than the one associated with the server through the user registration.
  With such an ability, we will be able to improve the client and server performances, reduce the bandwidth and improve some screens like the "Admin / Update Center / Nuxeo Studio" page.