docs: Rewrite deployment guide

docs: Rewrite deployment guide

The existing deployment could do with a little bit of fleshing out.
Do this, adding notes about the possibility of sidestepping much of
the process using deployment tools or PaaS solutions.

This also drops notes on deploying using MySQL/MariaDB or non-Ubuntu
distros. While it would be good to cover all use cases, it simply
isn't practical. Do one thing and do it well, providing notes for
users who want other options.

Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>
Suggested-by: Thomas Monjalon <thomas.monjalon@6wind.com>