Added extensions to drakcore and drakpush.

[kscieslinski]

Drakrun expects that the extension is passed in task header. I've also moved timeout, start_command and override_uid from task_resources to task_payload as this is what drakrun expects.

[icedevml]

In the frontend we have feature to manually specify the file name. Previously it applied to the full file name (i.e. file name WITH extension) so I suppose this is broken right now.

I think user should still be able to override the full file name (including extension).

[kscieslinski]

In the frontend we have feature to manually specify the file name. Previously it applied to the full file name (i.e. file name WITH extension) so I suppose this is broken right now.

I think user should still be able to override the full file name (including extension).

This should be fine. We ask user only for filename but later on in drakcore/app.py upload endpoint and in drakrun/drakpush.py we divide the filename to filename without extension and extension. This is because drakrun requires so (for routing).