docs: updated logo and fixed bad img refs (rackerlabs#526)

* Update infrastructure-design.md

Removed duplicate lines referencing wrong image filenames.

Corrected image filenames where appropriate to avoid 404s

* Add files via upload

Uploaded 2 new Logos

* Update index.md

Altered Logo Code

* Update cloud-onboarding-welcome.md

Updated Logo

* Update deployment-guide-welcome.md

Updated Logo

* fix: apply suggestions from code review

Confirmed these look fine in my browser after rendering with mkdocs. Nice!

Co-authored-by: Kevin Carter <[email protected]>

* fix: remove trailing whitespace from page

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Co-authored-by: Luke Repko <[email protected]>
Co-authored-by: Kevin Carter <[email protected]>