Bug 1024893 - [dolphin][v1.4]Entering settings app takes more than 2.2s

This patch reduces the Settings startup time by more than 1.5 second on Flame by doing several things:

- Load `root` list inline during build time, by removing the dependency on the JavaScript chain that does it dynamically. This way we don't have to wait for JavaScript to do that, and the settings list is ready right away. In order to accomplish this, a new attribute `data-inline-template` has been introduced.
- Removes `link` elements that are meant for tablet only during the build process, because it spent a lot of time (more than 200ms) executing the media query code in there. In order to accomplish that, a new attribute `data-device-type` has been introduced.
- Removed unnecessary background-color setting on the html and body elements (see https://bugzilla.mozilla.org/show_bug.cgi?id=1036446). Color is already set on the children elements anyway.

The difference can be seen in the following video: https://www.youtube.com/watch?v=IVHp0w7wW1Q

/cc @janjongboom
I would suggest simply move the root panel from `elements/root.html` to here. Then we could specify `current` as the class name and also add `data-rendered` to mark the section is currently used and rendered.