Website: consistent titles

[june-andronick]

(This may wait for the Information Architecture feedback first)

The titles on the landing page, top menu and individual pages should be made consistent. It's more confusing than it adds value to have them different.

For instance:

• "What is seL4" vs "About seL4" (I would keep the latter)
• "Stay in touch" vs "Contact information" (I would keep the former)
• "Commercial Support" vs "Services endorsed by the Foundation" (I would keep the former)
• "Use" vs "Retrofitting and transitioning to seL4" (I would revisit this page)
• "Support seL4" vs "Support us" vs "Funding the next big steps for the seL4 project" (I would keep the first)
• "Want to know more" vs "More information about seL4" (I would revisit and maybe merge with About seL4)