bbb-lti v0.1: Joins can be differetiated by the role in the LMS

...s/org/bigbluebutton/web/controllers/ToolController.groovy

...rg/bigbluebutton/web/services/BigbluebuttonService.groovy

...services/org/bigbluebutton/web/services/LtiService.groovy

...i/src/java/org/bigbluebutton/api/BigBlueButtonServer.java

bbb-lti/src/java/org/bigbluebutton/lti/Role.java