WIP: Merge duplicated documentation

• Link all to the generic pleroma install+configuration
  • Alpine Linux
  • Archlinux
  • Debian
  • CentOS
  • Gentoo
  • OpenBSD
  • NetBSD
  • Debian:Japanese @lambadalambda / @hakabahitoyo
  • OpenBSD:Finnish @eal
• Change the instructions to be similar to each others
  • Only keep sudo/su in how to change user paragraph, prefix with # when supposed to be launched as root, $ when supposed to be launched as pleroma, % when it doesn’t matter
  • OpenBSD: pleroma user is named pleroma, not _pleroma
  • Pleroma’s git clone is at ~pleroma/pleroma and pleroma’s home is at /opt/pleroma (At least for the linux distros)
  • Link to non-nginx example configuration files
  • pleroma’s default shell is /bin/false
• Proofcheck all the installation instructions
  • Alpine Linux
  • Archlinux
  • Debian
  • CentOS
  • Gentoo
  • OpenBSD
  • NetBSD
  • Debian:Japanese @lambadalambda / @hakabahitoyo
  • OpenBSD:Finnish @eal