fixes #4314 Don't let "admin" users see all other users in Piwik

config/environment/test.php

core/Access.php

core/Piwik.php

plugins/UsersManager/.gitignore

plugins/UsersManager/API.php

plugins/UsersManager/Controller.php

plugins/UsersManager/UserAccessFilter.php

plugins/UsersManager/UsersManager.php

plugins/UsersManager/javascripts/giveViewAccess.js

plugins/UsersManager/javascripts/usersManager.js

plugins/UsersManager/lang/en.json

plugins/UsersManager/stylesheets/usersManager.less

plugins/UsersManager/templates/index.twig

plugins/UsersManager/tests/Fixtures/ManyUsers.php

...s/UsersManager/tests/Integration/UserAccessFilterTest.php

plugins/UsersManager/tests/Integration/UsersManagerTest.php

plugins/UsersManager/tests/System/ApiTest.php

...d/test___UsersManager.getUser_login1_when_adminaccess.xml

...st___UsersManager.getUser_login1_when_superuseraccess.xml

...ed/test___UsersManager.getUser_login1_when_viewaccess.xml