Add bulk MODS export and MODS/EAD export fixes.

Added the ability to bulk export in MODS XML format, fixed issues
with the MODS export template, made site base URL an AtoM setting,
and fixed issues with EAD export.
Add alternative id column to CSV import #7388
Make createActor static, fixes PHP strict warning
Check archival history visibility in adv. search

Fixes #7417
Change condition
Fix alternative identifiers deletion, fixes #7418
Analyze alt. iden. labels in ES index, fixes #7419
EAD export: track IDs for fields with special roles, refs #5094

These fields may eventually be recombined into a single RAD event;
unifying them by ID allows them to be recognized on reimport.
EAD export: track IDs for events with relationships, refs #5094

On a reimport, this ID will be used to reassociate these date events
with their actors and places. Only track the ID if there are
relationships to reassociate later.
QubitInformationObject: return actors, terms, events when creating
EAD import: don't create relations for terms with IDs, refs #5094
EAD import: reassemble dates, actors, and places, refs #5094
Populate siteBaseUrl in configureSite, refs #7415
Added per-repo page to show popular descriptions.

Added a repository-related page that lists the most popular descriptions
in a repository and allows page views to be filtered by date range.

Added a method, to support paging through calculated result data, to
QubitPage to return result rows, rather than objects.
Simplified repo popular page routing.
Fixed issues with site base URL conf. Refs #7437

Added explanation for base URL setting field on site configuration
and site settings pages. Fixed issue with base URL saving during
installation. Added notification is site base URL not set.
Add job scheduling support, refs #239

- AtoM can now perform asynchronous tasks with the QubitJob class
- New job status/management page under manage->jobs if user is
  logged in
Regenerate model classes
Use default base url for --demo in tools:purge
Don't clear search when losing focus, ref #7352