Improve user roles

[CPapadim]

It is unclear how to set users to roles. Accounts are automatically assigned the same permissions if they are logged in. Allow configuration of roles and permissions for each account.

Admin account should be part of the file config (e.g. the way editors are). Other account roles should live in the DB and be configurable by the web GUI or by a command line script.

[CPapadim]

Roles:

Admin - Lives in Repo config, not DB. Has access to everything
Editor - Can create posts + everything View Only use can do
View-Only - Can view and subscribe to posts / tags

Add Role column to user table. Permissions per role will be hardcoded