[Alarm]: Implementation of Tizen alarm API.

This commit implements the Alarm API:
  https://developer.tizen.org/dev-guide/2.2.0/org.tizen.web.device.apireference/tizen/alarm.html

There is a known issue about repeat alarm: if the working system time zone is set to Daylight saving time like PDT or EDT, the repeat alarm finds 3600 seconds gap on the initial trigger time.

BUG=XWALK-428
incorrect indent and style here, suggest change as below
```
AlarmInfo(int id, EAlarmType type, int date,
          int delay, int period, int weekflag)
    : id_(id), type_(type), date_(date), delay_(delay),
      period_(period), weekflag_(weekflag) {}
```