[Tizen][Extensions] Implemented W3C SysApps Device Capabilities API

The implementation is based on 17 October 2013 editor draft version.
CPU, Memory, Storage and Display are included, the Audio and Video Codecs
are not implemented yet.

SPEC=http://www.w3.org/2012/sysapps/device-capabilities/
BUG=https://crosswalk-project.org/jira/browse/XWALK-47
Merge pull request #982 from qjia7/device

[Tizen][Extensions] Implemented W3C SysApps Device Capabilities API