[Tizen] Fix inconsistency in manifest handlers naming

This patch renames:
 - navigation_handler.h/cc to tizen_navigation_handler.h/cc,
 - navigation_handler_unittest.cc to tizen_navigation_handler_unittest.cc,
 - NavigationHandler to TizenNavigationHandler,
 - NavigationInfo to TizenNavigationInfo,
 - NavigationHandlerTest to TizenNavigationHandlerTest.
[Tizen] Fix allow-navigation WGT configuration element handler unit test

This patch adds unittest_util.h/cc in manifest_handlers directory, which
introduces a simple way for default W3C and WGT widget configuration creation.