chromium-build app now renders merged console from stored rows.

chromium-build app now renders merged console from stored rows.

This is the full change to get the chromium-build app to render the merged console from individual rows rather than from full pages. It is mostly a rewrite of the logic in console_merger to handle fetching individual row data and passing it to the ConsoleData object, which is then inserted into the template.

This CL puts the row-based rendering flow at feature-parity with the current console. The next, much smaller, CL is a series of small changes to handler.py and a few surrounding files to add proper url query parameter handling and to pass the user's ?rows=# request through to the merger.

This CL also rewrites the console_merger tests to accurately test the new row-based system, and removes the utf8 test as it is covered by console_handler_utf8 and parse_master. The app in this form passes all unittests here and renders the page identically to the current version when run inside dev_appserver.