Validation step before executing (batch) task

[GoogleCodeExporter]

A task cannot execute if not all of its parameters are provided by the 
parameter space. It would be helpful if the Lab could check before running a 
task or batch task if all parameters are always provided for every task - kind 
of a dry-run before actually running the whole stuff. That would avoid having 
users re-run everything in case a parameter was missing.

Original issue reported on code.google.com by richard.eckart on 17 Apr 2012 at 4:50