Fix substitutions for supervisions

See merge request !396

Show events with current changes in substitutions table

See merge request !394

Resolve "Show only teachers with courses in the current school term"

Closes #274

See merge request !395

Load avatar of affected teachers

See merge request !392

Resolve "Adapt to active school term"

Closes #260

See merge request !380

Merge branch '263-loading-animation-for-timetable-object-select-on-left-side-of-timetables' into 'master'

Resolve "Loading animation for timetable object select on left side of timetables"

Closes #263

See merge request !393

Resolve "Jump to first lesson instead of current time in timetables"

Closes #273

See merge request !390

Fix change detection in automatic plan

See merge request !391

Resolve "Make substitutions table more compact"

Closes #271

See merge request !389

Resolve "Don't show monday on sundays"

Closes #272

See merge request !388

Fix empty querysets

See merge request !387

Resolve "Permissions for timetables are not checked properly"

Closes #251

See merge request !369

Resolve "Hide days"

Closes #264

See merge request !385