azure-providers.js: Transition to /login for AzureAPI.login
azure-providers.js: Transition to /login for AzureAPI.login

Catch up with azurestandard/api-spec@61bba865 (public.json: Add a
POST-based /login endpoint, 2015-05-20).

azurestandard/azure-angular-providers,azurestandard/azure-angular-providers