Update docs for v1.4

Description

Closes issues: None Related issues: LA-93

Most important changes:

• Renamed "User manual" to "User interface" to better reflect the content (organised by pages/sections in UI).
• Added section "Concepts" to separate in-depth explanation of topics that are not immediately visible to the end-user. Includes:
  • Workflows (moved from manual)
  • Filtering (edited and moved from manual)
  • ACMG rules engine (moved from technical)
  • Gene panels (edited and moved from technical)
• Added changes for new/changed functionality in v1.4, updated various UI screenshots.
• Updated release notes for v1.4
• Many smaller changes to structure/content

Notes to reviewer

Check release notes in particular.

Type of change

• New feature
• Breaking change
• Bug fix
• Improvement

Tests

General

• Tests have been added that prove my fix is effective or that my feature works
• Related tests have been modified/removed

Hypothesis testing:

• Soak testing has been done
• Distribution between positive / negative cases has been checked

Database

• Includes changes to database schema
• Includes necessary database migrations

Configuration

• Includes changes to configuration
• Includes configuration migration instructions in documentation

General

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My branch has recently been updated with new changes in dev before this merge request
• I have made corresponding changes to the documentation