added navigation twig extension
removed preview from navigation and implemented navigation function
added tests for twig extension
added get breadcrumb in navigation mapper
Merge branch 'develop' of git://github.com/sulu-cmf/SuluWebsiteBundle into feature/twig-navigation

Conflicts:
	Navigation/NavigationMapper.php
	Resources/config/services.xml
	Tests/Unit/Sulu/Bundle/WebsiteBundle/Navigation/NavigationTest.php
added constructor argumentsto config
Merge branch 'develop' of git://github.com/sulu-cmf/SuluWebsiteBundle into feature/twig-navigation
fixed non existing level exception
Merge branch 'feature/twig-navigation' into develop