fixed EDU-314 Good code is bad: lesson 5 task 4: allow condition checking with is
fixed EDU-313 Good code is bad: leeson 5 task 3: allow check with not
fixed EDU-312 Unclear test failure message for lesson 4 / task 7
fixed EDU-311 Incomplete check for lesson 4 / task 6
fixed EDU-310 Unclear error message for lesson 3 / task 8
fixed EDU-309 Incomplete check for lesson 3 / task 6
fixed EDU-307 Overstrict check for the lesson 6 / task 3
fixed EDU-306 Unclear test error message when setting wrong color in lesson8 / task 3