Merge pull request #5207 from owncloud/fixing-4011-part2-master

apps/files/ajax/upload.php

apps/files/js/file-upload.js

lib/private/connector/sabre/exception/entitytoolarge.php

...rivate/connector/sabre/exception/unsupportedmediatype.php

lib/private/connector/sabre/file.php

lib/public/files/entitytoolargeexception.php

lib/public/files/invalidcontentexception.php

lib/public/files/invalidpathexception.php