Remove acl9, replace with SimpleRole

acl9 gem is a little bit opaque, had (at least one) rails 4.1.x incompatibility, and its tests are written in a convluted style with Test::Unit. Since our needs are simple (see what I did there?), rewrite, as SimpleRole, only implementing the methods that we use, and hardcoding (would be simple to generalize, but there is no need) class names for associations.

note, b/c there's some funny business with application ownership, DO NOT MERGE until we update the data.
So, here's a big gap in my Ruby/Rails knowledge: why the mixins/extend/include here? Why not just have all this in `lib/simple_role.rb`?