Remove current conf banner, componentise, document on reuse

[mtheoryx]

Here is the plan:

• Remove the LCC3 site-wide banner
• Create a conf site-wide banner for future use
• Add a link to the nav (header/footer/etc) for the static lcc3 page)

To enable:

• In the future, that banner can be used quickly
• A static page can be deployed quickly
• Future iteration is an index of conferences, each conf has a page, and a single "conferences" link in nav