Pgwar loopback

[joschne]

This PR integrates the pgwar into /server and /client

• it drops schema war
• it adds missing triggers to pgwar.entity_preview
• it adapts loopback (server) and angular (client) to
  • the new schema name pgwar
  • the renamed column in pgwar.entity_preview (project_id->pk_entity)
• it adds a script /database/dev.sh to start a complete dev db (without need for dev-stack)
• it updates /database/README.md about the usage of dev.sh