Expand role detection to support Blackboard's LTI implementation

I found that Blackboard prefers to send the Instructor role within the
"urn:lti:role:ims/lis/" URN. The support was already here, I just
extended the detected roles. Hooray for Blackboard support in
BigBlueButton!
Update bbb-lti README to note trailing slash issue

Save yourself hours of LTI debugging! Copying/pasting the URL bbb-conf
--salt brings along a trailing slash, which bbb-lti does NOT
appreciate. :)
Allow LTI to pass custom welcome messages
fix deskshare preview when the area is wider
implemented mute all functionality
the presentation window has been added to the layout.xml file and is properly positioned
fixed bug 1393 and properly formatted the MIC_SETTINGS_CLOSED event throughout the client
Adding recording support to the LTI middleware Grails app

When configuring an LTI consumer, pass [custom_]record=true to indicate
whether the session should be recorded.
added showbutton to deskshare module
Merge pull request #94 from kishba/master

Verified changes that work with Blackboard's LTI support.  Thanks!
Merge pull request #99 from SenecaCDOT-BigBlueButton/implement-mute-all

implemented mute all functionality
Merge pull request #100 from SenecaCDOT-BigBlueButton/add-participants-to-layout

the presentation window has been added to the layout.xml file and is pro...
Merge pull request #101 from SenecaCDOT-BigBlueButton/fix-sharewebcam-toolbarbutton

fixed bug 1393 and properly formatted the MIC_SETTINGS_CLOSED event thro...
 - upgrade to red5 r4581
 - initialize shared objects not on roomstart but on room connect
 - eject all users from voice conference when meeting ends
 - in listeners's module, listen for eject user event and make sure that the user is
   also ejected from the voice conf
 - in participants module, make sure the user is ejected from the voice conf when
   ejected from the web
Merge branch 'master' into upgrade-to-red5-r4580
 - upgrade to red5 r4582