Overview of all register objects

Closes #137

See merge request !152

Fix rules syntax

See merge request !159

Resolve "Fix usage of user.has_perm with object permissions"

Closes #143

See merge request !157

Merge branch '147-check-permission-rules-if-they-handle-lessons-with-substitutions-correctly' into 'master'

Resolve "Check permission rules if they handle lessons with substitutions correctly"

Closes #147

See merge request !158

Update ci config

See merge request !156

Merge branch '136-full-register-printout-show-only-weekday-in-first-column-of-lessons-table' into 'master'

Resolve "[Full register printout] Show only weekday in first column of lessons table"

Closes #136

See merge request !155

Resolve "Data checks ignore events and extra lessons"

Closes #145

See merge request !153

Merge branch '146-register-object-view-uses-non-existing-var-lesson_period-instead-of-register_object' into 'master'

Resolve "Register object view uses non-existing var lesson_period instead of register_object"

Closes #146

See merge request !154

Resolve "URL "lesson" does not exist and thus can't be resolved"

Closes #144

See merge request !150