Section DS processes all entries in memory even when no entry nodes are rendered

[allen]

Steps:

1. Create a DS that pulls from a section with many entries.
2. Limit the entries by 1000.
3. Check the pagination info checkbox but don't select any elements to output.

Result:

The DS still processes all the entries unnecessarily.

Correct Behaviour:

The DS should not process (SQL + processing overhead) over entries as they will not be required for XML output.