Improve memory usage of evaluator

[andrews05]

This adds a new final_round parameter to the evaluator, which allows us to determine when to keep the filtered data and when to keep the compressed idat_data. By only keeping one of these we can significantly improve memory usage.

Ref #683

[andrews05]

Some stats on a set of 10 large files. 8a44cdbc is the commit prior to refactoring optimize_raw which caused higher memory usage in 9.1.4.
At o6 the memory usage drops back to what it was before, while at o2 (fast mode) it's even lower than it was before.

memory -sao6
       75.70 real       680.67 user         2.76 sys
          2081685504  maximum resident set size
          1791613376  peak memory footprint

memory -sao2
       11.64 real        65.60 user         1.25 sys
          2752004096  maximum resident set size
          2214273280  peak memory footprint

memory -sao2 -t1
       59.53 real        58.39 user         0.76 sys
           551501824  maximum resident set size
           303793792  peak memory footprint

master -sao6
       74.11 real       680.50 user         2.79 sys
          3215491072  maximum resident set size
          2571888128  peak memory footprint

master -sao2
       11.62 real        65.42 user         1.24 sys
          3314466816  maximum resident set size
          2761025024  peak memory footprint

master -sao2 -t1
       59.11 real        58.32 user         0.76 sys
           644005888  maximum resident set size
           323684288  peak memory footprint

8a44cdbc -sao6
       74.44 real       682.79 user         2.83 sys
          2097070080  maximum resident set size
          1723193408  peak memory footprint

8a44cdbc -sao2
       11.63 real        65.88 user         1.21 sys
          3353853952  maximum resident set size
          2744837632  peak memory footprint

8a44cdbc -sao2 -t1
       59.32 real        58.52 user         0.78 sys
           697843712  maximum resident set size
           359794560  peak memory footprint

[AlexTMjugador]

Nice catch!