Tidy up theme setting logic when some settings do not exist.  Fix enablecustomlogin logic to be the default when the setting is unknown.
Merge branch 'master' of https://github.com/moodleman/moodle-theme_elegance
Merge pull request #5 from gjb2048/master

Tidy up theme setting logic when some settings do not exist.  Fix enablecustomlogin logic to be the default when the setting is unknown.