[ENH] Add numbers to the deployment instructions

[surchs]

Steps to be numbered:

0. Install dependencies / tools to deploy (see #142)
1. Configure the config files
2. Launch the stack
3. Go through the first time deployment config
4. Test the deployment

Notes from Thomas: Add a first step (step 0) / or a heading to install dependencies: docker, docker-compose, plus whatever else you need. This should always be at the start of an installation page (normally under a brief intro of what you are about to install).

Other documentation pages should also be checked to ensure any links to previous un-numbered sections of the infrastructure.md page are updated.

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[surchs]

Closed in #189