add global_navigation lti extension

test plan:
* modify an lti app xml to be configured
for the 'global_navigation' extension

* add the tool to a domain root account using
the modified xml
* should add a new link item to the global menu header

* edit the xml to add a property to the global_navigation
 extension:
<lticm:property name="visibility">admins</lticm:property>
* configure another tool for the domain root account
* confirm that the new link item is only visible
 for teachers and account admins

closes #CNVS-13815

Change-Id: I5ce42515ebc545d6f14bdc9dd628e1740b94d667
Reviewed-on: https://gerrit.instructure.com/39060
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>