Implement accept_resulsts_delay method for tasks

[badb]

For tasks there should be a added subtask_id and delay_time as an argument. The name should be also changed from "accept" to "set down" or something similar. The result of this method is a delay value, not a boolean as a name is suggesting.

[mfranciszkiewicz]

IMHO we don't need this method in an async environment. Also, this parameter might be irrelevant in a new assignment scheme.

[paulperegud]

I'll try to write down the scheme ASAP