Disable contextual autoescaping of Soy templates

Contextual autoescaping is considered deprecated by the Soy team, as
it makes it too easy to turn off autoescaping. Instead, use the new
"strict" mode, which disallows directives like |noAutoescape and |id.
This is safe for us as we weren't using them in any meaningful way
anyway.

Change-Id: I687e345c90aa38af6b0b936b8b5b5e5fe86f4ed8
10 files changed