Create a new core plugin allowing to mark bookmarks to read them later.
When enabled:
* checkbox is displayed in editlink view for new bookmarks
* a plugin setting is available to check it or not it by default
* in bookmark list:
* new global filter to display only bookmark flagged as read it
later
* for each bookmarks, new action icon to toggle read it later status
* for each « readitlater » bookmark, red label « To Read » added,
and red line on the right of the bookmark added (default template)
Fixes#143
Signed-off-by: ArthurHoaro <arthur@hoa.ro>