Feature/rails3 remove bundled acts as list

This removes the vendored acts_as_list and replaces it by referencing a current acts_as_list via Gemfile.

Doing so fixes some compatibility issues with rails3 (acts_as_list and default_scope in one model).

I am not sure why the project enumerations needed to be adapted after that. I assume, it is because the default order is now adhered to.