Because the isAccessibleByUser method can be run in contexts where $INFO
is not available, an explicit check is needed.

The permissions are now checked also when trying to the title of the
plugin.

This was previously carried out in three separate places. Refactor
that code to use the new function.

Update tpl_pageTitle test to use a manager level admin plugin.

add unit test coverage

Template authors now can use tpl_sidebar() to include the sidebar.
Sidebars can be defined in subnamespaces as well