PLEASE! Don't merge this pull request

 - Solved problem in view institution.
 - Add attribute active for students.
 - Change the button color to red iff the student or member is disabled.

 - I can't add comments in lines on github... 
     1. people_datatable.rb In line 41 the condition "if name!="Pers."" is ugly, it is because the method 'try' not work correctly.
     2. courses_student.rb In line 12 'before_update' not work.
     3. schema.rb I forget remove the line 72 "t.integer  "registered_count"" this field no longer be used