Create empty HTML files for all pages

These have routing specified via app.yaml, with adjustments to Grunt for
building.
Basic mustaching structure setup

This does not yet include the error and redirect templates, nor is
children data supported yet, but the gist of it is in-place here.
Add child navigation support

This is done by maintaining a pointer to the parent node when recursing
down the sitemap.
Restore error and redirect HTML pages

Mustaches these files and adds the transformation logic to Grunt.