[#5] Add error summary to harvest_job_dictize

It will return the counts for the 20 most common errors for that
particular job. These will available when calling harvest_job_show.

Also refactor the harvest source status object to just call
harvest_job_dictize on the 'last_job' key, as it has all the
interesting fields anyway.
Update template with new harvest source status
Add command for reindex all harvest sources
[#5] Add job summary page

Shows dataset and error counts, job details and a summary of the more
frequent errors.
[#5] Preliminary job report logic function and page (WIP)
Update job keys changed on 9ba6e8f
[#5] Add helper function for generating a link to a harvest object
[#5] Add method for returning the original URL for a document

Harvesters implementing IHarvester can define a `get_original_url`
method that should return a URL pointing to the original location of a
document in the remote server. If present, this URL will be used on the
job reports.

Examples:
* For a CKAN record: http://{ckan-instance}/api/rest/{guid}
* For a WAF record: http://{waf-root}/{file-name}
* For a CSW record: http://{csw-server}/?Request=GetElementById&Id={guid}&...
Document  method and cleanup the interface file
[#5] Fix typo in delete auth function
[#5] Change default auth for showing and listing jobs

Forward auth checks to harvest_source_update instead of
harvest_source_show, as job reports should only be visible to users that
can manage sources.
[#5] Cleanup the job controller actions
[#5] Add new finished field for harvest job

When the run command flags a job as finished, it will query the most
recent harvest object for this job and use its import_finished value as
the job finishing time.
[#5] Update report templates

The job details page has been updated to show the full error report, and
the whole report page has been dropped. All job details are loaded via a
snippet, which is also loaded on the harvest source page.

The frontend is still completely provisional.
[#5] Add job listing page
[#5] Allow not returning error summary on job dictize
Fix typo and add missing column on v3 migration script
Merge branch 'release-v2.0' into 2.0-dataset-sources
Merge branch '2.0-dataset-sources' into 4-new-auth-for-2.0
Merge branch '4-new-auth-for-2.0' into 5-improve-job-errors-reporting