Re #346: DelayedJob to purge harvested Europeana records no longer in the portal.
Re #346: Europeana record purge job:
* check that API response indicates successful request
* test only for items in response to indicate continuation
Re #346: Update Solr index after each batch of deleted Europeana records purged.
Re #346: Rake task to queue EuropeanaPurgeJob with DelayedJob.
Re #348: DelayedJob to update harvested Europeana records.
Create a DelayedJob logger.
Europeana purge/update jobs for dry runs.
Re #348: Check if local record has been updated more recently than remote.
Re #346: Modularize DelayedJobs for maintenance of harvested Europeana portal records.
Re #348: Account for Europeana API timestamps being in milliseconds.
Re #348: Handle empty Europeana update log file.
Re #346: Uncomment record deletion in purge job.
Re #346, #348: Expire cached Europeana record EDM on update and deletion.
Re #348: Uncomment Europeana record re-harvest in update job.
Cache paths to Europeana records in search results, not URLs.
Re #346: Remove unnecessary Solr commit from Europeana record purge job.
Re #346: Optimize purge job, dry run.
Re #346: Uncomment destroy action in optimized purge job.
Re #346, #348: Restore Solr index update to Europeana update and purge jobs.
Re #348: Rename update log file to prevent log rotation.