Add a default admin group
Add an error template

This template contains only a back button and displays the error messages of flask.flash
Only show the options to create a package or a collection is the user is a pkgdb admin
Add the error page itself
Add the is_admin decorator as well as the is_pkg_admin and is_pkgdb_admin methods

The @is_admin decorator is meant to restrict access to the page only accessible to
pkgdb admin, for example: create a collection or a package.

The is_pkgdb_admin is a simple function returning a boolean whether the user is part
of the admin FAS group set in the configuration file.

The is_pkg_admin is returns boolean whether the user has approveacls rights on a
specific branch of a specific package.
Bundle the @fas_login_required decorator and handle case where user isn't logged in

The @fas_login_required decorator has been bundled as we do not have a 'auth_login'
method but a 'login' one.
Handle case where the packager searched does not exists
Update collection namespace

When displaying the list of collections, the option to create a new collection is only
visible to the pkgdb admins.

Handle case the collection does not exists, to display an error

Restrict the new collection page to pkgdb admins.
Update packages namespace

When displaying the list of packages, the option to create a new packages is only
visible to the pkgdb admins.

Restrict the new packages page to pkgdb admins.

Handle case the package does not exists, to display an error

Retrieve for each branch of a package if the current user has 'approveacls' rights, so that
we can display the link to update ACLs only if they are allowed.
Display options for a package to user logged in and link to update ACLs to people w/ the rights
Start implementing the authentification/authorization in the ACLs