[Tizen][Linux] Support the following URI schemes: tel:, sms:, mailto:.

Explanation:

1 Override "content::RuntimeResourceDispatcherHostDelegate::HandleExternalProtocol" in according child class to implement the platform-specific surpporting:
    (1) On TizenIVI, through DBus to invoke corresponding default system application.
    (2) On Linux, use XDG utils.
    (3) On Android, it's been implemented already, keep unchanged.
2 In "XWalkContentBrowserClient::ResourceDispatcherHostCreated" triger the resource_dispatcher_host_delegate to be set.
3 The main reason to implemented the Linux part is to verify our design, the code of function "XDGUtil" is copied  from chrome directly. 
BUG=https://crosswalk-project.org/jira/browse/XWALK-1501
The "tel" is a standard URI, but there is not standard actions defined of how to deal it through Browser(Web Runtime), by my investigation. My idea is pretty straightforward that now we just launch the system default "Call" page with the phone number.