Add Hardware documentation

From http://www.vodafone.com/content/index/about/what/devices/smart4mini.html

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
README.md: Add Vodafone Smart 4 mini HW specs
Merge pull request #1 from gmacario/add-hw-docs

Add VF Smart 4 mini phone HW documentation