Increment version number to 4.3.0 (Alpha).

Readme.md

-# STACK 4.2
+# STACK 4.3
 
 [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.
 
@@ -6,23 +6,18 @@ STACK was created by [Chris Sangwin](http://www.maths.ed.ac.uk/~csangwin/) of th
 
 STACK is based on continuing research and use at the University of Edinburgh, the Open University, Aalto, Loughborough University, the University of Birmingham and others.
 
-
 ## Current state of development
 
-STACK 4.2 contains some important new features, a number of interface improvements and bug fixes.
-
-**Note: please read the release notes before upgrading from STACK 3.X to STACK 4.X.  STACK 4.0 represents a major release of STACK and is a non-reversible change, with important differences which break back-compatibility. Especially, note the [conversion of old materials](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Authoring/ImportExport.md#migrating-stack-3-questions-to-stack-4).**
+STACK 4.3 contains some important re-engineering of core components.  This will enable significant new features in future releases.
 
 Please continue to report any bugs you find at https://github.com/maths/moodle-qtype_stack/issues.
 
 The [current state of development](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Developer/Development_track.md) is explained more fully in the [developer documentation](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Developer/index.md).
 
-
 ## Documentation
 
 The [documentation is here](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/index.md), including the [installation instructions](https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Installation/index.md).
 
-
 ## License
 
 Stack is Licensed under the [GNU General Public, License Version 3](https://github.com/maths/moodle-qtype_stack/blob/master/COPYING.txt).

version.php

@@ -24,12 +24,12 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2019052700;
+$plugin->version   = 2019072900;
 $plugin->requires  = 2015111600;
 $plugin->cron      = 0;
 $plugin->component = 'qtype_stack';
-$plugin->maturity  = MATURITY_STABLE;
-$plugin->release   = '4.2.1 for Moodle 3.0+';
+$plugin->maturity  = MATURITY_ALPHA;
+$plugin->release   = '4.3.0 for Moodle 3.0+';
 
 $plugin->dependencies = array(
     'qbehaviour_adaptivemultipart'     => 2018080600,