[WIP] view decorator to check authorization

Alternative approach for  [C2C #188450].

Instead of defining every ressources to *protect* on the varnish side, we may only let varnish set a custom header `X-Searchserver-Authorized`to `true`or `false` and protect the view ( `height`, `profile.json|csv` and ogcproxy) by a custom decorator.


Compare:

    $ curl -I "http://localhost:9001/rest/services/height?easting=600000&northing=200000"
    HTTP/1.1 403 Forbidden
    Content-Length: 193
    Content-Type: text/html; charset=UTF-8
    Date: Thu, 02 Oct 2014 09:29:34 GMT
    Server: waitress

with:

    $ curl -I -X "X-Searchserver-Authorized: true" "http://localhost:9001/rest/services/height?easting=600000&northing=200000"
    HTTP/1.0 200 OK
    Connection: close
    Content-Length: 16880
    Content-Type: text/html; charset=UTF-8
    Date: Thu, 02 Oct 2014 09:30:26 GMT
    Last-Modified: Tue, 30 Sep 2014 10:07:44 GMT
    Server: waitress


Mapproxy:

Access is OK:

    $ curl -I --resolve mf-chsdi3.dev.bgdi.ch:80:127.0.0.1  -H "X-Searchserver-Authorized: true"  "http://mf-chsdi3.dev.bgdi.ch/ltmom/mapproxy/service?REQUEST=GetCapabilities"
    HTTP/1.1 200 OK

and forbidden:

    $ curl -I --resolve mf-chsdi3.dev.bgdi.ch:80:127.0.0.1   "http://mf-chsdi3.dev.bgdi.ch/ltmom/mapproxy/service?REQUEST=GetCapabilities"
    HTTP/1.1 403 Forbidden