Implment can_feature, can_publish and can_approve methods

[giohappy]

The logic to enable/disable these actions is currently spread all over the GeoNode codebase, making its maintenance and reuse hard or impossible.

The following methods will be implemented under the security.utils.py module:

• can_feature(user, resource)
• can_approve(user, resource)
• can_publish(user, resource)

For each of them a proxy method will also be implemented inside the Profile model e.g. Profile.can_approve(resource) -> security.utils.can_approve(user, resource).

can_approve/can_publish

These methods will implement this logic and they will replace all the blocks of code, similar to this one, where the logic is repeated.

can_feature

For the moment we will restrict the permission to set a resource as featured to superadmins only.
Same as for can_approve and can_publish, this control will replace the inlined controls.

EDIT: we already have AdvancedSecurityWorkflowManager.is_allowed_to_publish and AdvancedSecurityWorkflowManager.is_allowed_to_approve. We should probably base security.utils.can_approve(user, resource) and security.utils.can_publish(user, resource) on these, and they should be adapted as the following:

• is_allowed_to_publish: it shouldn't rely on a static publish_resourcebase Permissions, as it is now. This permissions, as well as the approval permission, should be calculated dynamically. Having a static publish_resourcebase doesn't make sense, and it should be removed in the future.