Support wagtail-localize: show language next to page titles

[cluck]

When using wagtail-localize, pages get duplicated, while retaining their title (see screenshot 1). The wagtail-transfer source/target chooser dialog is not well prepared for this situation, showing multiple identical entries to choose from (screenshot 2). It would be great, if wagtail-transfer could be extended to display the language tags as in the first screenshot.

Screenshot 1:

Screenshot 2: