Compute jobs with multiple datasets & selectable compute env

[LoznianuAnamaria]

• Receive multiple parameters in the startCompute function
• Also added compute env as an argument for computeStart function - Fixes #36

[bogdanfazakas]

Looks good to me.

@bogdanfazakas is there any reason why we haven't merged this?

nope, just wanted another pair of eyes to check it, since i added one or two commits as well