Add navigation links to Previous/Next books in the series

[nclm]

I very often find myself to want to jump quickly from one work, to the previous or the next one in the series. It would be great to add some navigation links for that in Inventaire!

• It already has the data from the series ordinal property.
• It could additionally also fetch the information from the follows and followed by properties.
• There could be as well a way to consolidate all these properties behind the scenes (like adding the missing ones, inferred from the existing ones), but really out of the scope for this issue, this is just about a UI element :)

[nclm]

Made some suggestions in #413