Improve the documentation for running in production

[jniles]

The BHIMA documentation for installation is pretty good and has seen several revisions. It is found at https://docs.bhi.ma/en/for-developers/installing-bhima.html.

This documentation is mostly meant for getting developers up and running, and isn't ideal for running in production. We should add a separate set of instructions for running in production that covers:

1. Using nginx as a proxy so that users don't have to type the :$PORT after the url in the web browser.
2. Setting a strong SESS_SECRET variable in the .env
3. Setting up backups using cron.

Some optional stuff we might consider adding:

1. Setting up .my.cnf so that system administration is easier.
2. Encouraging systemd over pm2.

[jmcameron]

@jniles Shouldn't this have been closed by your recent Debian set up PR?

[jniles]

I suppose it could be. I would like to keep working on these issues though. It probably won't be as relevant if I can get the server to build with docker-compose.

[jniles]

I did get the application working with docker-compose, so I'm closing this issue.