Go through the Request Credentials guides and update for major release changes

[localredhead]

Please base your branch and PR from this feature/did-major-release

• [ ] update request credentials for the proper amount of detail, omitting unecessary inclusion of chasqui, etc.
• [ ] remove or replace outdated or inaccurate content.
• [ ] ‘calling the request method’ should be a link to a guide about transports. (transports link TBD)
• [ ] the verify credentials section does not need to be added anymore
• [ ] attesting credentials graph is too much detail

[mi-xu]

Pages to update: https://developer.uport.me/requestcredentials https://developer.uport.me/gettingstarted
https://developer.uport.me/attestcredentials https://developer.uport.me/signtransactions