[Alarm] Initialize the "id" to null in constructor
The alarm id becomes valid only when it's added into tizen system.
Before that we should ensure the property is enumerable.
Set the configurable to true because we can re-define the property later in sub class when it's added into tizen system.

BUG=XWALK-2127
[Package_api] Initial implemenation

Add package instance skeleton code
validate arguments
Install / Uninstall
Adding getters/setters
cstor + dtor(PackageManager create/ destroy)
getPackage