Add Identity 1.5 docs

[eike-hass]

Description of change

Add docs for the 1.5 version, remove 1.3 docs and fix minor inconsistency 1.4.

Type of change

Choose a type of change, and delete any options that are not relevant.

• Documentation Enhancement

Change checklist

Tick the boxes that are relevant to your changes, and delete any items that are not.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own changes
• I have made sure that added/changed links still work
• I have commented my code, particularly in hard-to-understand areas