webapp_server works

This confirms that we can convert complicated templates (including #if, #each, and dynamic attributes) into HTML using Views.

Template#__lookup was moved to View#lookup, since webapp_server is an example of a case where we have lookup but no template!

Next steps: get rid of the “3” after some names, the OLDSTYLE flag, and dead code in the blaze package.  Then make Template features like events, `helper`, etc. work.