Use input() to get page number

Restricting page numbers to `$request->query->get()` makes it very hard to make api end points which can accept a big amount of filters via an HTTP request because there are several different limitations on how a GET request can function. Allowing current-page to be accessible via `$request->input()` makes it very easy to just send the page number along with a big post-data of all the filters.
update contributing.md
Merge pull request #4383 from veelasky/patch-2

update contributing.md
Merge pull request #4381 from kapv89/patch-9

Use input() to get page number
Merge branch '4.1' into 4.2
Merge branch '4.2'