Feat: Super admin - user management

[pranavxc]

Change Summary

• Root-level user management
  • org-level-creator role - this user can create a new project and access any invited project
  • org-level-viewer role - this user can't create a new project but they can access any invited project
• Token management
  • Newly created tokens are associated with the created user and it will have all permissions that particular user has
  • Existing token will work as it is and only be visible to the super admin
• Signup without an invite is disabled by default and can be managed from UI by a super admin.

Change type

• [x] feat: (new feature for the user, not a new feature for build script)
• [ ] fix: (bug fix for the user, not a fix to a build script)
• [ ] docs: (changes to the documentation)
• [ ] style: (formatting, missing semi colons, etc; no production code change)
• [ ] refactor: (refactoring production code, eg. renaming a variable)
• [ ] test: (adding missing tests, refactoring tests; no production code change)
• [ ] chore: (updating grunt tasks etc; no production code change)

Test/ Verification

Provide summary of changes.

Additional information / screenshots (optional)

Anything for maintainers to be made aware of

[pranavxc]

@wingkwong

1. This new page is for managing users globally(only available for super admin) and differs from project-level user management.
2. If invite-only signup is enabled only invited users can signup. And if a non-invited user signed up they will have org-level-viewer role by default.
3. Newly invited users won't have access to any existing project unless the project owner or super admin is invited to the project. If we invite a user as org-level-creator then they can create a new project.

[pranavxc]

Nice to have a better UI and redirection to Sign In page after resetting password

@wingkwong: will do it in a separate PR