0.5 eulenspiegel release

[Jochen Garcke]

With the new release today we added a couple of new fields to our models.

The biggest change is the addition of issue variants. This mainly
concerns issues with different covers, be it with different artwork,
price, barcode, brand, etc. Issue variants will fetch most story
sequences from its 'base' issue, but they can have their own cover
sequence if the artwork is different from the base issue.
The two new fields for this are variant_of as a foreign key to the
'base' issue and variant_name to give the variant a name.

We added a barcode field to track UPC/EAN numbers.

For European series or TPB series we added an issue title field in
addition to the issue number.

Leading articles are now correctly handled for sorting without moving
them to the back of the series name. Series have an additional sort_name
field for that purpose.

We added an uncertain flag for series years.

ISBNs, barcodes, issue titles and indicia frequency can now be turned
off for a series using the has_field on the series level.

Added corresponding no_fields for ISBN, indicia frequency, barcode,
issue title on the issue level.

Jochen