Rename RootAccount to FreeArgs to be more aligned with the terms described in the manifesto

[f8122dac91]

The terms and naming convention used in the example, like "root accounts", are not defined and could cause some confusions.

We should demonstrate the idea more clearly:

• Rename RootAccounts to FreeArgs which indicates that these are free arguments which is the term used by the manifesto as well as the term argument indicating that it can be any information not just on-chain accounts.
• Define the terms and concepts used in the manifesto more clearly.

[f8122dac91]

WIP

Terms and conven to be defined:

• *Keys
• struct *FreeArgs, pub fn resolve()
• verify functions