Change the way the lti endpoint is configured and used

bbb-lti/grails-app/conf/Config.groovy

bbb-lti/grails-app/conf/UrlMappings.groovy

bbb-lti/grails-app/conf/lti.properties

...s-app/controllers/org/bigbluebutton/ToolController.groovy

...i/grails-app/services/org/bigbluebutton/LtiService.groovy