Refactor DataScroller for Performance and Fix Lazy Loading

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Current behavior
If the datascroller fires a lazy load event, it assumes an instantaneous, successful lazy load happens, thus immediately incrementing "this.first = this.first + this.rows;".
Since there is no way to unbind the lazy load event while lazy loading, a normal scroll finger movement will fire huge amounts of lazy load events... while the lazy load event you actually care about is not yet finished.

Expected behavior
Maybe allow deactiving the lazy load event while lazy loading. Seriously. Is there any use case in which in the current behaviour is required or useful? What do i miss?

[Bohdan-Tereta]

Had a similiar issue, and fixed that, see my pull request #4676.

Please check and merge if you'd like.

[cagataycivici]

We'll implement virtual scroll for lazy mode.

[mroskamp]

@cagataycivici I'm still running into this issue in v5.2.4. Here's a plnkr where I introduce a 250 ms timeout before loading the next page of results, which illustrates the issue: http://plnkr.co/edit/5EyojPuaoLg9ox5olk4z?p=preview

[jonbarthol]

The Plunkr example posted by @mroskamp may not load. Here's the same example on StackBlitz:
https://datascroller-bug.stackblitz.io

I opened a new issue: #5816