Update HTTPS/SSL docs with wp-cli information

[benlk]

From something RC wrote in the helpdesk channel in Slack:

1. Update site domain to https at http://exampleorg/wp-admin/options-general.php
2. WP Engine Dashboard => Install page => SSL Tab => select "Secure all URLs"
3. WP Engine Dashboard => Install page => Advanced Tab => then run the following WP-CLI command wp search-replace http://example.org/ https://example.org/ --dry-run
4. Run the same command as above but without --dry-run attached

• [ ] update https://github.com/INN/docs/blob/ee53fd30061a1c77e89e6de274d694ff5461dad3/how-we-work/dev-processes/install-ssl.md with that information

[rclachance]

some things about :wpengine:'s WP-CLI interface:

1. after 26 seconds, your query times out on the front end. Needs re-running to verify it completed (sometimes dry-run is helpful as well to verify completeness)
2. they're missing some commands, such as wp db search, so I can't actually search the entire db for http://. I could, but I'd have no visibility what the results were, just a count of how many occurrences