Add export of KML

This is work in progress. 

[Testlink](http://mf-geoadmin3.dev.bgdi.ch/gjn_export_kml)

### Export from Drawing dialog
- [x] Points (including sizes)
- [x] Polylines (including coloring)
- [x] Polygons (including coloring)
- [x] Text -> will not be exported because of troubles with import. Seperate issue will be created.

### Export from measure dialog
- [x] All

### Integrate into feedback (allow to send drawing as kml)
**This needs https://github.com/geoadmin/mf-chsdi3/pull/1046 to work**
- [x] Sends existing drawing as kml attachement (see section about drawing dialog). Also works in IE9

### Todos
- [x] Download on IE browsers (IE9 is not supported)
- [x] Name of file
- [x] Translations
- [x] Help

### Refs
http://stackoverflow.com/questions/283956/is-there-any-way-to-specify-a-suggested-filename-when-using-data-uri
http://stackoverflow.com/questions/3749231/download-file-using-javascript-jquery
http://johnculviner.com/jquery-file-download-plugin-for-ajax-like-feature-rich-file-downloads/
http://stackoverflow.com/questions/7763505/is-it-possible-to-initiate-a-download-prompt-in-browser-for-recognized-mime-type

`node.outerHtml` is browser dependant and contains the node's kml in string format. In some browsers, outerHtml is undefined, in which case we use the XMLSerializer to transform the node into a string.

It's a browser detection mechanism. I'll add a comment.