change ConfigurationManager.AppSettings back to System.Environment.GetEnvironmentVariable because Kudu.exe doesn't have access to the same app settings as w3wp.exe
handling getting 403 in Ajax calls from JS by displaying an error and asking the user to refresh the page. Fixes #1146
return 400 instead of 500 on site extension install exceptions. Fixes #1411
When deploying a site extension deploy its WebJobs.
The site extension needs to have the WebJobs under `App_Data\jobs\{job type}\{job name}`.
The jobs will be moved (not copied).
The result WebJob name will be `{site extension id}({job name})`.
Fixes #1393