OO-3055: implements move of taxonomy level (for identifiers/keys path) and add a DELETE method for taxonomy level in REST API

OO-3108: close the file system created for zip files, set default encoding to UTF-8 for some stream to string operations

OO-3106: exclude large doc per default, fail fats if the index directory doesn't exists, remove print out

OO-2916: Better exception handling of unavailable cover images, more validations of page from/to, utf-8 of infodoc response

OO-3102: make to print view of test statistics works with the test resource and not only within a course

OO-3055, OO-3047: implementation of taxonomy module with new site, full text search, webdav access, REST API...