Fix installation of NPRuntime plug-ins.

Fix installation of NPRuntime plug-ins.

[Issue#] N/A
[Problem] All NPRuntime plug-ins are installed with a widget instead of
only those that match target architecture.
See "Tizen Web Runtime Core Specification 2.1", section "Web Application
Installation", requirements 0102 and 0103.
[Cause] N/A
[Solution] Provide API for retrieving path to the NPRuntime plug-ins
depending on the target architecture.
[SCMRequest] N/A

[Verification]
1. Build repository.

Change-Id: Ic341d91adc7a6019b4b0f330baaf06982a44eb8c