Add script for checking coding style

Uses cpplint.py from Chromium depot_tools. Since we all have depot_tools
to build Crosswalk, it is OK to depending on it.

For now all the directories are ignored so we can fix things gradually.
Fix common/ coding style
Fix notification/ coding style
Fix power/ coding style
Fix time/ coding style
Fix network_bearer_selection/ coding style
Fix tizen/ coding style
Add exception for system_info/

SystemInfo makes use of non-const references in its code. Add a filter
to ignore this for now.
[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`.
bluetooth: Fix freeing a NULL GVariant

When createBonding() or destroyBonding() fails, a NULL GVariant is
returned as a result, we should not try to free it in this case.
bluetooth: Fix crash when receiving a PropertyChanged with new devices

This signal is emitted when a previously unknown device connects to
the host, for example, when you receive a connection from a device
that is not already paired.
Merge pull request #112 from vcgomes/gvariant-fix

Fix crash when asking to pair a new device. Fixes #568.
[download] Fix bug which stops download being able to build for mobile
[SystemInfo] Support multiple frames. Fixed bug #113 #569
Fixed bugs in the event listening mechanism

1. Use g_source_remove to unregister the g_timeout_add event.
2. In destructor, check if exists active listening event. If true, stop listening.
Fixed memory corruption issue
Merge pull request #114 from qjia7/mymaster

[SystemInfo] Support multiple frames. Fixed bug #113 #569
[Systeminfo]Fix Desktop Build Error
Merge pull request #116 from fyraimar/master

[Systeminfo]Fix Desktop Build Error
Make 0.3 version as QA validated it.