Merge branch 'master' into szkopul
(no-ticket) Fix submitting in contests with participants

Change-Id: I6ad6c26d049054610350a04541652ecdcf5efbb2
Workaround for SIO-1266: force grappelli 2.4.4

Change-Id: I2508b162ad626ba78a7d6f64c602ea3ef40ef5c7
Merge branch 'master' into szkopul
Use threshold_linear_test_scorer in TeacherContest

Change-Id: Iec1008e9b299bb9d86c777fdc27fb8ff695b9062
Merge "Use threshold_linear_test_scorer in TeacherContest"