Add titles to OPDS acquisition links

[johnfactotum]

Currently, each entry has four acquisition links, but since the link to EPUB and the link to EPUB 3 have the same type, it's hard for the client or user to tell which is which.

Would it be possible to add an ttile attribute to the links containing short labels, like "EPUB", "EPUB 3", "Kobo", "Kindle"? I don't think the spec mentions this, but I've seen some OPDS feeds do this.

If there's a title, clients that support titles can provide a more useful way for the user to select a link, instead of showing two links with identical types.

[acabal]

Good idea, I've added titles in 6a176a8. Thanks!