Read-only Publish toggle on Entries

[duncanmcclean]

This PR fixes #1011 where if the 'manage publish state' permission isn't checked on a role and when a user in the role tries, they would be able to toggle the publish state.

This PR fixes this bug from the front-end by passing in a new can-manage-publish-state prop of whether or not the user has permission to manage publish state on that collection.

However it does seem like it could be a good idea to also enforce this on the backend side as well. What do you think?

[jasonvarga]

Thanks for the start on this. 👍

I've made some additions to this:

• apply the read only logic to the "create" form
• server side handling of the permission when saving an existing entry
• let it work within the entries fieldtype stack
• added a couple of placeholder tests as todos

[duncanmcclean]

Awesome!