Default roles and permissions for users

We need to define some default roles and permissions for these roles. Here's my thoughts so far:

Author

• Role can create, edit and delete own post content
• Role can publish own content

Editor

• Role can create, edit, publish, delete post content
• Role can add users and assign Editor role and Author role

Administrator

• Everything else

These 3 roles are already installed by default on a fresh install of the distro.