[demo] add system info demo

The added demo packages is:
   tizen-extensions-crosswalk-system-info-demo-${version}-${release}.${arch}.rpm
Install the package with `pkgcmd`, like:
   $ pkgcmd -i -t rpm -p tizen-extensions-crosswalk-system-info-demo-0.2-0.i586.rpm -q
More information about demos at commit `1ed2d38`.
Merge pull request #109 from legendlee1314/newdemos

[demo] add system info demo