Merge pull request #436 from pagespeed/jefftk-simplify-option-setting

options: refactor repeated code in option setting
static-handler: refactor to use write_handler_response

This fixes sending out the weak ETag for ngx_pagespeed_static/js_defer.hash.js,
and simplifies things somewhat for this code path.
It also adds a test for it.

Fixes https://github.com/pagespeed/ngx_pagespeed/issues/434
downstream-cache-test: don't hard code the port to 8051
Merge pull request #437 from pagespeed/oschaaf-downstream-cache-fix-test

downstream-cache-test: don't hard code the port to 8051
Merge pull request #435 from pagespeed/oschaaf-refactor-static-handler

static-handler: refactor to use write_handler_response
Refactor base fetch related functions.