Uneven long running task iimplementations

[sverhoeven]

trafficstars

The following ways have a long running task implementation

• Python web application
• JavaScript web service
• JavaScript web application

But the following ways don't

• Web service using Common Gateway Interface
• Python web service

To make the guide consistent we should have a long running task implementation for each way.

[sverhoeven]

@jspaaks has other suggestion:

long running tasks (concept, Python toolset, JavaScript toolset): consider splitting off into 1 or 2 separate documents; in the main document describe a what is basically a Promise and point to the relevant other document