extend Paginator to support infinite pagination and postgres estimated count

[Denis Cornehl]

We often have problems with bigger tables and slow {{count(*)}} performance.

depending on the use-case there are two ways to improve the situation

• just work without count, if you never show the page-count. Then the paginator can just return empty results if the end is near.
• use rough estimations for the page-count, perhaps with some security margin. For example PostgreSQL supports this by using {{EXPLAIN}}, based on the table statistics.

I want to

• extend the paginator to support both (infinite and estimate)
• provide an option for {{ModelAdmin}} that let's you use the estimation-paginator.
• or perhaps even support the infinite-paginator, this would also include interface changes to the pagination.