Simplified EWSGI interfaces

Renamed WGI_RESPONSE_BUFFER as WGI_RESPONSE to avoid confusion
Removed EWF_HEADER and removed related caller from WGI implementation,
   now this is only part of WSF library
Added wgi_version, wgi_implementation and wgi_connector to the WGI_REQUEST interface
   to give more information to the user
Added back WGI_CONNECTOR to WGI specification, mainly because of `{WGI_REQUEST}.wgi_connector'
   simplified WGI_CONNECTOR to contain for now only `name' and `version'
   if the implementation of connector inherit from WGI_CONNECTOR (recommended)
   this might gives more access to the user using a reverse assignment for specific needs
   (but this usage is not recommended due to portability issue on other connector)
Removed useless connector.ecf since now EWF/WGI library provides the helper classes

library/server/ewsgi/specification/request/wgi_request.e

@@ -129,6 +129,25 @@ feature -- Access: CGI meta variables
 		deferred
 		end
 
+feature -- EWSGI access
+
+	wgi_version: READABLE_STRING_8
+			-- Eiffel WGI version
+			--| example: "1.0"
+		deferred
+		end
+
+	wgi_implementation: READABLE_STRING_8
+			-- Information about Eiffel WGI implementation
+			--| example: "Eiffel Web Framework 1.0"
+		deferred
+		end
+
+	wgi_connector: WGI_CONNECTOR
+			-- Associated Eiffel WGI connector
+		deferred
+		end
+
 feature -- Common Gateway Interface - 1.1       8 January 1996
 
 	auth_type: detachable READABLE_STRING_8