Add drush command to check input

[mjordan]

It would be useful to be able to validate that the PIDs and the directories named in the input file exist. A command to do this would report any missing objects/directories, or empty directories.

[mjordan]

drush --user=admin islandora_batch_load_children_check_input --input_file=/tmp/test.txt now in place. To do: add the option to log the output to a file, not just the drush log console.