possibility to use run time subsitution on sos_describesensor_url

[assefa]

possibility to use run time subsitution on sos_describesensor_url.

The user could possibly have someting like %SensorID% as part of the value of
the metadata and that will be substitued with the value of SensorID passed as
part of the DescribeSensor request

[assefa]

add Tom in cc.

Tom what do you think of just using the same metadata sos_describesensor_url and
give it the possiblity is use the vaiables substitutions coming from the
request. I think It gives us more flexibility to do the patterning. 

[tomkralidis]

Sounds good to me. I think this will work.

So, for the code, if a sensorid (case-insensitive) parameter is found the 
DescribeSensor request, MapServer will process that putting that into the URL

So, example:

Request:

http://foo/foo?service=SOS&version=0.1.2b&request=DescribeSensor&sensorid=1234

MapServer:

If MapServer does NOT have LAYER/METADATA/sos_describesensor_url defined, then 
a ExceptionReport is thrown as the response.

If MapServer does have LAYER/METADATA/sos_describesensor_url defined, then it 
passes the sensorid parameter from the request to the HTTP Location directive.

"sos_describesensor_url" "http://foo/foo?mysensor=%sensorid%"

Does this make sense?

[assefa]

commited as described in comment #2. Will close att the bugs after tests.

[tomkralidis]

Tested.  Works.  

[tomkralidis]

P.S. this change should be documented.