Pre-release fixes for v0.9.0

[AlexandreDoneux]

Pull request containing multiple small fixes to merge before release v0.9

• [x] Inaccessible course after changing to combinatory test task dispenser
• [x] Combinatory test task edit : unable to feed modal
• [x] Codemirror : broken line number increment for code blocks (01,11,21,31,...)
• [x] Submission list : "Start page option is not defined"
• [x] Combinatory test : Obsolete functions used (ex: dispenser_util_get_weight)

[anthonygego]

LGTM