docs: make the resizable side nav standard. DO NOT MERGE.

This actually affects only
the SDK tab, which previously did not allow resizing---now it does.
Also add a couple new templates to allow either 190 or 200 pixel-wide
side navigation by default, and apply 200 to the Resources tab.

Change-Id: I4555c496088dd8aac77f9aa01273c3a1d52f89e0