feat: improve capabilities/roles granularity

[nicobao]

• give moderator rights to orgs for their own org conversations. Create a config variable to give this mod right to anyone creating a convos, not just orgs. Default to everyone. Follow the same configuration variable pattern as already implemented for import right. Important note : by default this moderation right only enables users to MOVE, not to hide. Create another conf variable to also enable HIDE.
• generally speaking move towards capabilities instead of roles. Create specific capabilities such as "I can move to history opinions from ALL convos site wide". "I can move to history only my own convos". "I can HIDE only opinions from my own convo". "I can LOCK any conversation". "I can LOCK only conversations from my specific organization".
  "I can manage organizations for everyone org-wide".
  Etc etc. Come back to me for specifics.