Detect and display rotten titles

[benoit74]

We need some solution to see rotten titles, i.e. titles for which a given title flavour has not been updated for very too long. Problem could be a title or flavour level obviously.

For that, we need to:

• add a filter in title view to search for rotten titles (titles which have a flavour which has not seen a new book for too long)
• just like article and media count, allow to customize the threshold to consider a flavour as "too old" per collection (with a global default in environment variable and if not set 13 months)
• enhance title flavour display (from Manage title flavours with dedicated API + UI #396) to show when each flavour has been updated, and wether it is too old or not