Introduce calendar type choice at system level

Install the calendar type 'test' ( https://github.com/markn86/moodle-calendartype_test ) into the folder calendar/type/test. Visit admin/index.php and install the 'test' calendar. Visit <yoursite>/admin/settings.php?section=calendar and set the calendar type default to 'test' (it should be 'gregorian' by default'). Enable self registration. Create a user using the registration steps and ensure that the calendar type set for their profile is 'test'. Create a user using the web service functionality and ensure the calendar type in their profile is 'test'. Log in using the DB authentication plugin and ensure the user is created with the 'test' calendar type. Create a webservice script (see https://github.com/moodlehq/moodle-local_wstemplate/tree/master/client ) to create a user with the 'gregorian' calendar type and check that they were created successfully with that calendar type. Create a webservice script to create a user without specifying the calendar type and check that the calendar type was set to 'test'. Create a webservice script to create a user specifying the calendar type as '' and check that the calendar type was set to 'test'. Create a webservice script to update a user's calendar type (who was originally set to 'gregorian') to 'test' and check that it was updated. Create a webservice script to update a user (but not their calendar type) and ensure there calendar type was not altered. Create a webservice script to update a user's calendar type (who was originally set to 'gregorian') to '' and check that it was not updated.