Theme: Move handlebars pages out of site folder

- Moves the theme content pages out of the site directory so they aren't
rebuild by the themes during the bower install.
- Slug-ify the content page names to differentiate word endings
- Don't i18n transform files with a lang specific file ending
Merge pull request #5364 from nschonni/move-theme-templates

Theme: Move handlebars pages out of site folder