Use API directly using CORS

To simplify our general setup, I attempted to get rit of our mod_proxy definitions in the apache configuration. CORS is supposed to support cross-domain resource loading. But IE9 does not support it using standard xhr requests (https://github.com/geoadmin/mf-geoadmin3/issues/26). With a workaround found in [1][2] and some fiddling around, I was able to get it to work completely...almost. Following issues remain:

1. ~~In **IE9**, the src path (debug mode) does not work anymore. I suspect that our overwriting of the XMLHttpRequest object conflicts with it's use in the closure dependency loader. A smart man would be able to solve this.~~
2. ~~In **IE9**, print is working, but the resulting PDF does not contain the map (all other elements are present). Related to missing referer. See below in the comments.~~
3. ~~In **IE9** and **IE10**, the ogcproxy (used in wms and kml imports) does not work. @oterral any idea?~~
4. ~~In **IE9** search does not work anymore (typeahead probably doesn't like the XMLHttpRequest overwrite~~
5. ~~In **IE9** profile drawing does not work~~

I've tested in IE9, IE10, Chrome 34 and FF 29 (not conclusive). **Safari and Mobile Browsers not yet tested.** You need https://github.com/geoadmin/mf-chsdi3/pull/830 on the API side for this to work and test properly..

Remark: Note that the XMLHttpRequest overwrite is only done for IE9. All other browsers ignore it.

[1] https://github.com/angular/angular.js/pull/1047
[2] https://gist.githubusercontent.com/MrOrz/6405400/raw/1a78269fd27e660395627809b60e28e88f56df0a/xdomainrequest.js.coffee