filter "slug" field from rails_admin

Otherwise, slug is assigned to "", and no slug is created.
import for chapters and problems
add chapter field to problem in rails_admin
[rails_admin] add ckeditor body field fo problems, solutions, comments
return 'acts_as_votable' to problem

Was removed, because it raised error during import in rails_admin
order chapters by number on textbook
user can't vote for own solutions and comments

[Delivers #55344432]