Allow setting page buffer and dataset chunk caches in units of pages and chunks

**Is your feature request related to a problem? Please describe.**
Setting page buffer cache or dataset chunk cache size as a number of file pages or dataset chunks, respectively, is sometimes more easier for users to understand. Currently, both cache sizes can only be set as the number of bytes which is not directly related to how many file pages or dataset chunks could fit in those caches.

**Describe the solution you'd like**
The library allows setting these two caches as numbers of file pages or dataset chunks. For example: page buffer cache size of 8 file pages, dataset chunk cache size of 16 chunks.

**Describe alternatives you've considered**
Open a file to find out its file page size in bytes, close, do the math of how many file pages to cache times the file page size, re-open again by setting the desired page buffer cache size in bytes. Similar for dataset chunk cache.