Add OpenLayers Protocol for CSW

[bbinet]

Included patch from pgiraud is adding support for Format CSW as an OpenLayers Protocol.

[bbinet]

The patch attachment:CSW_Protocol.diff provided by pgiraud needs OpenLayers CSW Format from Ticket #2132

[bartvde]

Thanks for this work Pierre, I've made a few minor changes, and issued a pull request:

 https://github.com/openlayers/openlayers/pull/136

would be great if you could have a final look. TIA.

[bartvde]

Forgot to mention that respective tests pass in Safari 5.1.2 and FF 8.0.1

[bartvde]

Btw, I've talked to ahocevar about including a protocol that does not return any features, and he did not see any issue with this approach since we also have formats that do not return features.

[ahocevar]

In with  https://github.com/openlayers/openlayers/commit/5393532f5897442496d93e82fde056228c63b4bd