Give content editors sweeping permissions to administer content

[phenaproxima]

I feel like the permissions of the content_editor role are a lot more fiddly than they should be. That could lead to inconsistency and weird bugs.

I think it makes sense to say that content editors should be fully in charge of content and can do anything to content on the site (nodes, taxonomies, blocks, media), regardless of bundle. Content editors shouldn't necessarily be in charge of site structure, but content? Have at it.

This PR removes the fine-grained permissions from the content editor role and replaces them with the broader "administer" permissions.

[pameeela]

I think ultimately the roles and permissions will undergo a lot of analysis and review before we land them. Given that, I don't want to hold things up, but I also don't totally agree with this. Usually we have a content admin role that is more along these lines, and a content editor role with more limited permissions. I guess since editor is the only one we have now, it makes sense to fix it up and worry about the rest later?

[phenaproxima]

The only reason I wanted to do this is because we don't have thorough test coverage of the current permissions, so we don't know if the content editors actually have useful permissions.

If you don't think this is a good idea, then I think it's fine to leave things as they are in HEAD for now...