Deprecates the function select_in_gradebook_tabs() in behat_grade.php.
After the tertiary navigation changes in gradebook this function became
obsolete and is now replaced by select_in_gradebook_navigation_selector().

The $CFG->grade_navmethod setting has been removed because it is not
required anymore. This setting was used to set the type of navigation
(tabs or dropdown box) which will be used in gradebook. However, these
navigation methods are no longer used and replaced with tertiary
navigation.

The functions grade_print_tabs() and print_grade_plugin_selector()
can be deprecated as they are no longer used. These functions were
used to generate and output the tabs and dropdown box navigation
in gradebook which is now replaced with tertiary navigation.

Added groupid to grade_plugin_return tracking, modified constructor
to use query params as defaults if passed-in params not supplied,
used groupid tracking in core reports.

grade_get_graded_users_select also fixed to use gpr (otherwise using
it breaks when course current group has changed between render and
submit).

Fixed coding style issue in gpr constructor & documented properties.

Added upgrade.txt noting gpr changes.