[ClassContent] + updated CategoryManager::loadCategoriesFromClassContentDirectories() to use AClassContent constants
[Rest] + fixed PageController::getCollectionAction() which returned wrong 'Content-Range' in response headers
[Rest] #62 + added 'GET classcontent definition route' and 'GET classcontent definition collection route' to ClassContentController
Merge branch '62': [Rest] close #62 + added 'GET classcontent definition route' and 'GET classcontent definition collection route' to ClassContentController