docs: new section "Installing and running Invenio"

[lnielsen]

Purpose of section is to get newcomers started gently on how to install and run Invenio (i.e. a bit more depth than quickstart but not too much either)

• Bootstrap (i.e. what are the script doing)
  • Python dependencies, NPM, building assets, static files.
• Setup (i.e. what are the script doing)
  • Cache, Database, Index, MQ
  • PostgreSQL + Elasticsearch versions
• CLI
• Running the development server
• Running the worker
• Configuring Invenio
• Upgrading the database
• Users and permissions
• Administration interface