Add Apache mod_unique_id's identifier in WebProcessor

mod_unique_id can add a unique ID to every request and also add it to other logfiles. This makes it easy to correlate lines from different logs belonging to the same request. http://httpd.apache.org/docs/2.2/mod/mod_unique_id.html
Update WebProcessorTest.php
Update AbstractProcessingHandlerTest.php
Add unique_id to extra data only if present in the server environment
Merge pull request #247 from mpdude/patch-1

Add Apache mod_unique_id's identifier in WebProcessor