Update jumbotron

* Defaults to no rounded corners and full width in the viewport
* When in a container, the jumbotron has extra padding and will have
rounded corners
* Updates default jumbotron example to show the full width default
display

Fixes #9759.
Favicon in navbar example
Navbar update

Addresses a few different cases where the navbar has and doesn't have a
container, and accordingly adjusts the padding and margin of key
elements.
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip