Update the docs for the 4.2.2 release.

Readme.md

-# STACK 4.2
+# STACK 4.2.2
 
 [STACK](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/About/index.md) is an assessment system for mathematics, science and related disciplines.
 

doc/en/Developer/Development_history.md

@@ -2,6 +2,16 @@
 
 For current and future plans, see [Development track](Development_track.md) and [Future plans](Future_plans.md).
 
+## Version 4.2.2
+
+Released September 2019.
+
+* Removed the Maxima MathML code (which wasn't connected or used).
+* Add in metadata system to the documentation (Thanks to Malthe Sporring for this suggestion).
+* Add in extra option `simp` to inputs.
+* Add in extra options in the input `allowempty` and `hideanswer`.
+* Review and updated documentation (thanks to Malthe Sporring).
+
 ## Version 4.2.1
 
 Released August 2018.

doc/en/Developer/Development_track.md

@@ -7,14 +7,6 @@ How to report bugs and make suggestions is described on the [community](../About
 
 ## Version 4.3
 
-DONE:
-
-* Removed the Maxima MathML code (which wasn't connected or used).
-* Add in metadata system to the documentation (Thanks to Malthe Sporring for this suggestion).
-* Add in extra option `simp` to inputs.
-* Add in extra options in the input `allowempty` and `hideanswer`.
-* Review and updated documentation (thanks to Malthe Sporring).
-
 TODO:
 
 * 1st version of API.