minor: LDPPermissions overhaul

Closes #305 (closed) #297 (closed) #328 (closed) #329 (closed) #295 (closed) #343 (closed) #197 (closed) #325 (closed)

See issue #305 (closed) for full description. Fixes various permissions bugs, cleans everything up & removes buggy functions like user_permissions

Partial fix for #291 (closed)

TODO:

• code redesign
• tests for #291 (closed) and #297 (closed)
• performance tests
• extending unit tests
• reintroduce or remove permissions cache
• MRs for packages
• documentation (guides)
• release notes
• merging DjangoLDPv2
• superuser permissions

Related MRs in packages

• djangoldp-i18n!12 (merged)
• djangoldp-invoice!11 (merged)
• djangoldp-circle!39 (merged)
• djangoldp-project!48 (merged)
• djangoldp-community!2 (merged)
• djangoldp-notification!39 (merged)
• energie-partagee/djangoldp_energiepartagee!2
• djangoldp-contact!1 (merged)