Sync core counts from Task to Job

[mfansler]

Problem

The number of cores requested via Job constructor is independent of the number of threads actually used by the task, resulting in the end user having to know what to specify based on knowledge of the run.sh internals, or already specifying a thread count elsewhere (e.g., entities file).

Possible solution

Create a reserved keyword argument to be used in .task files to specify the default number of threads used in the module. If no cores parameter is specified by user in Job instantiation, default to that of the task.