Restructure menu and clean up content links

[snehankekre]

Restructures the menu / table of contents in line with ideas proposed by the DevRel Team.

The purpose of this PR is to preview a build of the docs with the restructured menu. The restructuring effort is a work in progress and should not be merged until there is a consensus on what the menu should look like.

[randyzwitch]

Added the .keep file to kb for the time-being to remind myself this folder needs to exist. I have the hierarchy on my local branch, will start to populate it and push on Wednesday

[snehankekre]

• Updated line 2 of sources.list as make docstrings was breaking
• Updated docstrings with make docstrings
• Corrected RefCard href for all st commands to point to the right location. E.g. replaced <RefCard href="/library/api-reference/layout#columns"> with <RefCard href="/library/api-reference/layout#stcolumns">
• Removed deprecated beta_ prefix from API

[randyzwitch]

Merging this today, so that the PR doesn't get any larger. Going forward, we'll make much more atomic PRs, and in the case of content-only changes, the DevRel team will self-manage those PRs.