website: more css tweaks
- make it so prev-next bar is bottom-aligned, even if the
content doesn't fill the window height
- move component positioning rules to index.less so that
it's clear how the main components are positioned relative
to each other
- tweak a few of the markdown pages that had headings inside
info/warning boxes so that those headings wouldn't be so
large.
Unrelatedly, this CL makes a few adjustments to the text
content.
Change-Id: I3d8db348df44c265c7bbf26b14a42e7ebf331535
12 files changed
