Fix the background of the login page
Import Original and Supporting files separately

This change modifies the import side to assume that the export side
knows which files are originals and which are supporting and exports
them as two distinct columns.

This allows us to attach them as the right kind of uploads preserving
the public visibility (i.e. ReadLevel) of the files as they were in the
old system.

We attempt to parse works out of *all* files (because, why not?) and
stop upon first successful parse. Typically, we'll either find works in
the first original file or not find anything at all.
Fixed FindFieldGroup to correctly parse field_groups
Add a default "action_taken" to Importer::Base, allow nil
Adjusted what OtherParser handles

Some files say just "legalother", not "legalother2"
Add parsers for blogger and eb dmca form emails
Guard against NilClass#split
Register new importers
Ensure file exists before opening it
Refactor blogger parsing a bit
Save suporting files in LegacyCsv::ErrorHandler