Added SVG fallback to apps settings popup

This fix issue of calendar app with IE8, see issue report for details:
https://github.com/owncloud/calendar/issues/291
Useless else removed

As suggested by @PVince81 : https://github.com/owncloud/core/pull/6721#issuecomment-32289922
Merge pull request #6721 from tsumi/patch-1

Added SVG fallback to apps settings popup