Add APL-related items (#6652)

* Add one APL book

And fix links and notes the some others

* Add APL cheat sheets

* APL courses

* French APL video series

* mark APL Course as in process, add one more course

* mark as in process

* ADSP and Array Cast

* Add APL

* Add APL-related entries

* Add number for sort ordering

* correct number of blank lines between last section and next heading

* Remove trailing slash

* Move book

* Move book and limit URLs to 1 per line

* full URL

* add missing line

* Combine into playlist

* replace multiple links with single link

… which is a redirect to the listing for the latest released version

more/problem-sets-competitive-programming.md

@@ -11,6 +11,7 @@
 
 * [4Clojure](http://www.4clojure.com)
 * [A2 Online Judge](https://a2oj.com)
+* [APL Problem Solving Competition](https://contest.dyalog.com)
 * [AtCoder](https://atcoder.jp)
 * [beecrowd](https://www.beecrowd.com.br)
 * [Binary Search](https://binarysearch.com)
@@ -84,6 +85,7 @@
 * [A2 Online Judge](https://a2oj.com/ps)
 * [Advent Of Code](http://adventofcode.com)
 * [Anarchy Golf](http://golf.shinh.org)
+* [APL Practice Problems](https://problems.tryapl.org)
 * [BaekJoon Online Judge](http://www.acmicpc.net)
 * [beecrowd](https://www.beecrowd.com.br)
 * [CareerCup](http://www.careercup.com)