Added Super Admin role and WHMCS login
Added ability to login directly with WHMCS credentials (on Airtime login
screen)
Fixed missing constant
Fixed bad client ID / subdomain check in WhmcsLoginController
Fixed syntax error... grumble grumble
Super Admin edit page points to billing now

* Also prevent super admin from being deleted
Set up CORS for microsite autologin after signup
Merge branch 'whmcs-login' into cc-5709-airtime-analyzer-buy-now
Add billing section to main menu