Fix typo
Make replace_version_string global

This is so I can use it in the manifest page to get the current
major version number.
[manifest] Add manifest overview page
[manifest] Add sub-pages for field descriptions
[manifest] Add permissions info and field descriptions
[manifest] Sort sub-pages alphabetically
[manifest] Crosswalk 1 didn't support Android
[manifest] Reposition anchor as it's causing incorrect styling of the heading
[manifest] Start populating sub-pages