Request that migrate_log gets a more complete picture. [#2460433]

Unfortunately migrate-import and its supporting logs does not provide an easy way to get created records after the operation; besides being present to get the drush output of

Processed 776 (60 created, 716 updated, 0 failed, 0 ignored) in 248.6 sec (187/min) - done with 'IIRProject'

This sample output from a migration is not easy to get at another time ie.. there is currently not a database record to get this output information. the obvious spot of getting the record is the table `migrate_log` but it only has number of records processed.

+------+--------------+--------------+---------------+---------------+------------------+----------------+--------------+
| mlid | machine_name | process_type | starttime     | endtime       | initialhighwater | finalhighwater | numprocessed |
+------+--------------+--------------+---------------+---------------+------------------+----------------+--------------+
|    1 | IIRAsset     |            1 | 1425954552570 | 1425955727140 |                  |                |         6234 |
|    2 | IIRProject   |            1 | 1425955794430 | 1425955814800 |                  |                |          197 |
|    3 | IIRAsset     |            1 | 1425957649350 |          NULL |                  | NULL           |         NULL |
|    4 | IIRProject   |            1 | 1425958194640 | 1425958221210 |                  |                |          197 |
|    5 | IIRTaround   |            1 | 1425958237740 | 1425958238960 |                  |                |           35 |
|    6 | IIRProject   |            1 | 1426010163110 | 1426010241210 |                  |                |          764 |
|    7 | IIRTaround   |            1 | 1426010265180 | 1426010274500 |                  |                |          317 |
|    8 | IIRProject   |            1 | 1427401253742 | 1427401502342 |                  |                |          776 |
+------+--------------+--------------+---------------+---------------+------------------+----------------+--------------+

It would be helpful to have another column to contain "(60 created, 716 updated, 0 failed, 0 ignored)".