Fixed various CMS_MODULE.install, by not marked module installed if an error occurred!

Improved Auth related module implementation by having a way to change settings like token, max age.
  - use CMS_SETUP.site_id and related "auth.$module.token" ... configuration values.
  - removed related CMS_..._CONSTANTS classes.

For auth session module, use auth_session as table name, and use VARCHAR(64).
Extracted sql from blog module, and store it under site/scripts/install.sql .
Renamed a few $modulename.sql as install.sql

examples/demo/modules/demo/cms_demo_module.e

@@ -70,8 +70,9 @@ CREATE TABLE tb_demo(
 						api.logger.put_error ("Could not initialize database for demo module", generating_type)
 					end
 				end
-				Precursor {CMS_MODULE}(api)
 			end
+				-- For this demo, be flexible, and do not required sql.
+			Precursor {CMS_MODULE}(api)
 		end
 
 feature -- Access: router