Improve cfg parameter inheritance hierarchy

[forsyth2]

#204 showed that default values provided in subtasks will override values a user provides higher up in the inheritance hierarchy. This may not be the best behavior. Perhaps the following hierarchy would be better:

1. Defaults in [default]
2. Get overridden by defaults in [climo], [ts], etc.
3. Get overridden by user-provided values in [default]
4. Get overridden by user-provided values in [climo], [ts], etc.

Note that the current order is 1>3>2>4 (steps 2/3 are flipped). 1>2>3>4 would mean users have the final say whereas the current 1>3>2>4 means the tasks/subtasks have the final say.

[forsyth2]

1>2>3>4 would mean users have the final say whereas the current 1>3>2>4 means the tasks/subtasks have the final say.

"2. Get overridden by defaults in [climo], [ts], etc." > "3. Get overridden by user-provided values in [default]": proposed change -- advantage: a user's settings will propagate throughout the tasks/subtasks.

"3. Get overridden by user-provided values in [default]" > "2. Get overridden by defaults in [climo], [ts], etc.": current hierarchy -- advantage: since different tasks/subtasks may have different default values, a user will have to consciously change the task/subtask value, even if setting a default at a higher level.

I believe we agreed that the current hierarchy is sufficient. Closing this issue.