Add support for monitoring allow-navigation occurrence.

Add support for monitoring allow-navigation occurrence.

[Issue#] https://bugs.tizendev.org/jira/browse/TDIS-6856
[Problem] All allow-navigation elements from web application's
configuration document are parsed but only the first one should be
processed.
[Cause] N/A
[Solution] Add flag for monitoring whether allow-navigation element has
already occurred.
[Verification]
1. Build repository

[Notes]
Utilized in configuration parser (in wrt-installer).

Change-Id: I9f67822ada3fc547d02ac80c08d595281740b91c