Save records with system_user
Make importer file validation DRY
Don't fail early on null csv string conversion

This change allows the uploading of a poorly formatted csv to fail in
the correct place, during file validation, not during row processing,
where it was choking on empty cell values.
Make file validator fail and exit in one place
Refactor saving without auth to only allow sysuser

For security purposes.
Merge pull request #1791 from steventlamb/topic/save_bulk_imports_with_system_user

Topic/save bulk imports with system user