Fix structure, titles, and gaps in multi-tier setup documentation

[sbrossie]

• Reorder steps so database creation happens after EC2 instances are launched, fixing a bug where the doc had you SSH into an instance before it existed.
• Rename "Create the Database Manager" -> "Create the RDS Instance" and "Create the Databases" -> "Create the Kill Bill and Kaui Databases" to distinguish the RDS instance from the schemas created inside it.
• Fix "Setup X" -> "Set Up X" verb misuse and title-case inconsistencies across section headings.
• Fix broken [.no-title]# formatting in the SSH-removal NOTE.
• Link the SSH login step to the shared how-to-login-to-your-ec2-instance doc instead of duplicating instructions inline.
• Add missing instructions in 7.4 to set the second ELB listener's protocol to HTTPS and attach a certificate (previously unstated, even though Step 8 tests over https on that port).
• Add public-subnet/auto-assign-IP explanation for consistency with the single-tier doc, and a "What You Will Need" summary table matching the CloudFormation doc's pattern.
• Fix two stale cross-references in the maintain doc broken by the renumbering/renaming above.
• Also added a 'What you will need section':

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