WMS should support vendor specifc parameters

[tomkralidis]

See patch submitted by Servais Nabil

I would like to suggest 2 patchs. The first is for supporting custom parameters of WMS, I don't know if it's normalize by OGC, but it's supported by Mapserver.

For exemple I have this request in openlayers:

http://wmshost/cgi-bin/xyea?LAYERS=oursindep%2Cetablissement&FORMAT=jpg&IDOURSIN=%20uai_dger%7C%7Cinsee_resplegal%20%7C%7Cfiliere_code%7C%7Csecteur_pro_code%7C%7Coption_code&GROUPBYCLAUSE=%20GROUP%20BY%20%20uai_dger&WHERECLAUSE=%20WHERE%20secteur_code%20%3D%201&GEOMSUFFIXE=_rel&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A27572&BBOX=-679807.84,1230100.62,1925309.84,2987770.38&WIDTH=996&HEIGHT=672 And this is the request with my owslib patched :

url_wms = ' http://wmshost/cgi-bin/xyea' layers = [ 'oursindep', 'etablissement', 'responsables_legaux', 'regions']

    bbox = (-10.900634765625, 36.857250976562, 15.400634765625, 55.742749023437)

styles = custom = {'WHERECLAUSE':'WHERE secteur_code = 1',

        'GROUPBYCLAUSE':'GROUP BY uai_dger',

            'IDOURSIN':'uai_dgerinsee_resplegal filiere_codesecteur_pro_codeoption_code'}

img = wms.getmap(layers=layers,

styles=styles, bbox=bbox,

    size=(1197, 859),

format='image/jpeg', srs='EPSG:4326', custom = custom )

Alternatively, could use the same implementation as WCS. To decide.

[tomkralidis]

Duplicate of #9