Feature request: renamable course and lessons

[vitalii-kaplan]

Now names of lessons and course can not be changed.
It is really frustrating because we need to add lessons about frontend development to the course with name "Deep Java".

[mehanig]

Lesson renaming added in branch https://github.com/mehanig/stepic_server_django/tree/fixes

[vyahhi]

Also courses cannot be created by the user.