Add horizontal pagination for views

[pannal]

GHI (If applicable): #

Description:

• adds pagination for episodes in season views (fixing performance issues with big seasons, e.g.: anime)
• adds pagination for onDeck items in postplay
• adds pagination for related items everywhere - increasing the related item count to 36 (artificial limit, PMS API "bug" reported)
• 8 items per page by default and 4 possible orphans per side

Known issues:

• related items PMS API query is slow, hence the artificial limit
• related items PMS API results order is inconsistent (using the same offset/start value doesn't yield the same results for the next page)

Checklist:

• I have based this PR against the develop branch

[pannal]

Possible followup PR:

• make page size and orphans configurable via advanced setting
• make artificial related item limit configurable as well?

[pannal]

Found an off by one. Fixing it tomorrow.

[pannal]

Good to go.

[ruuk]

Looks good, except I think it would be better if we keep some of the current items when you page, so you have a page size and window i.e. if the window size is 16 and you had 8 and you added 8, 16 would be showing. If you add 8 more you take 8 off the beginning and have still a window of 16 showing. This would allow correcting the list jump after paging by first selecting an item in the wrong direction and then the correct item so that the focus position in the end remains on either the right or the left depending on where it was before the page.

[pannal]

I've added an initialPageSize attribute, which is set to 18, and increased the orphan count to 8, so an initial load would not paginate for 26 items. Afterwards it continues with pages of 8 with an orphan size of 8 (at the beginning or end of the list).

[pannal]

@ruuk we should probably still set a lower page size for related items and extras, as those requests take considerably longer. I'd go with 8+4 in those cases.

[pannal]

Commit 8114d11 is semi-related; it depends on this PR, though.