/api/quest: sort, limit and offset options
extract common cgi and paging code from collections
/players: replace progress bar with spinner; show spinner on load more
remove useless logging
Collection.WithCgiAndPager now guesses whether there's more data to fetch
improve user-collection
extract progress view from user-collection
/explore pager
new show-more style (row instead of button) in quest-collection
new style pager for /players
Merge branch 'quests-pager'
increase /players page size to 100
'... and N more' note if there're too many likes
offset and limit for /api/event
style show-more rows as .success
refactor quest/collection and user/collection common code into proto-paged
/feed "show more" button