Consolidate all user-facing KA Lite website stuff into FLE site

This is an extension of https://github.com/fle-internal/fle-site/pull/42 .  I've refactored things to be more self-encapsulated, similar to the recent work on the `ka-lite` and `ka-lite-central` projects.

**NOTE that the setup procedure has changed; please run `./manage.py setup` to complete setup (including loading fixtures--if you have data, this will probably overwrite them!)**

From here, I am planning to make the following format and content changes:
* Adding a `product comparison` table
* Making `extended features` visible in the navbar--too important to embed in a sub-page.
* Fleshing out `join our community`
* Making `partner with us` clear that it is focused on funded, large-scale partnerships.

And longer-term goals:
* Making it clear that support is being offered through public documents and community, not interactively by us.
* Finding ways to more strongly / consistently brand with KA Lite logos and colors.

Please join in!  Let's try and get this completed by the time @dylanjbarth is back!