WIP: Feedback attachment

https://github.com/geoadmin/mf-geoadmin3/issues/1522

Current implementation accepts only one attachment.
Similarly to the Import KML, this feature is not available in IE9.

[Test Link] (http://mf-geoadmin3.dev.bgdi.ch/gal_feedback_attachement/src/?X=202235.27&Y=752102.91&zoom=1&lang=en&topic=ech&bgLayer=ch.swisstopo.pixelkarte-farbe)


The click redirection could be done in similar fashion to what we already have in importkml directive:

See https://github.com/geoadmin/mf-geoadmin3/blob/master/src/components/importkml/ImportKmlDirective.js#L229-L237