Security-server new API for privilege checking

Security-server new API for privilege checking

[Issue#]       SSDWSSP-527
[Feature]      Introduce two new SS API functions.
[Cause]        New API will improve the performance while checking
               app privileges.
[Solution]     Two new functions in client API enable to check whether a given
               app or caller app has enabled permission specified by name.
               Modified service: app-permissions.
               Two new sockets added to systemd and affected service.
[Verification] Build, install & run tests.
               Verify together with new libprivilege database.

Change-Id: If8d4efd30bbf22f82cd1442256ccbe7efb68a8aa