Added Omnibox and Off-Road Mode sample extensions and references

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Added stuff for new APIs

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Merge pull request #63 from shwetank/master

Additions to declare_permissions and sample extensions pages