File-system backend fixes and support JWT

[igk1972]

- Summary

The need for Netlify-CMS to work with a remote file-system backend.
In plans, implement a standalone backend on nodejs and go lang. With the generation of jwt tokens.

- Test plan

• Run yarn build.
• Download and run preview api code in from https://gist.github.com/igk1972/367b68b26495f47c1b571cdd38f720c5

- Description for the changelog

• remove obsolete file logo.
• update AuthenticationPage - html & css.
• add support netlify identity - jwt token.
• fix tokenPromise - not work with fetch.

[verythorough]

Deploy preview for cms-demo ready!

Built with commit 5929454

https://deploy-preview-1029--cms-demo.netlify.com

[verythorough]

Deploy preview for netlify-cms-www ready!

Built with commit 5929454

https://deploy-preview-1029--netlify-cms-www.netlify.com

[talves]

Note: A branch for having external register of a backend has been proposed here as #1011

• I have successfully exported the file-system backend for use using Register Internal and Custom backend API's #1011 with a couple caveats.

@igk1972 I think this is a viable solution and good idea. Not sure the development targeted file-system would require auth. Needs discussion.

I have also created a stand alone express server solution for using the file-system and realized the requirement for a stand alone server will be project specific and should stand as a project/solution on it's own.

Takeaways:

• Discussion for the development file-system File System API (Final On-Hold) See Comments #786 being removed to an external backend should be discussed
• This is definitely a solution that should be exported to make a stand alone server using a backend to support file-system with auth.

cc/ @erquhart , @Benaiah , @tech4him1

[igk1972]

@talves then I will focus on go lang implementation stand alone server.

[talves]

@igk1972 you could use the example backend repo as a skeleton and export your solution into an external backend. Use #1011 as the cms build to test it.

ping me in chat if you have any questions on how to setup the registerBackend

[erquhart]

@talves should we close this?

[talves]

Yes, this should be closed. There is now a solution to be able to take this to an external backend.

#1011 has been accepted, so this solution can be exported like my example. Note the cms-server branch also.