Fix inconsistent section structure/order throughout docsite

[martriay]

Right now we have this inconsistent section structures throughout the docsite:

Upgrades

1. explainer
2. usage

Account

1. interface

Access

1. usage
2. interface

ERC20 and ERC721

1. interface
2. compatibility
3. usage

Security

1. usage

Introspection

1. interface
2. usage

---

I think we should have

1. explainer
2. usage
3. compatibility

and leave interface for API, of have it between explainer and usage.

@andrew-fleming suggested:

ERC721Component

• Implementations
  • ERC721Impl
  • ERC721MetadataImpl
    ...
• ERC721 compatibility
• Usage
  ...