add username to the signout button

[MynockSpit]

Description of changes:

Put username in navbar.

Additional changes:

• also rename unused cognitoUser to user
• clarified some of the auth functions use and when they happen

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[MynockSpit]

Travis completed successfully. Merging.