Update OpenLoco version to v20.03.

CHANGELOG.md

@@ -1,4 +1,4 @@
-19.03+ (in development)
+20.03 (2020-03-23)
 ------------------------------------------------------------------------
 - Feature: [#347] Screenshots are now saved in PNG format.
 - Fix: [#226] Zooming to cursor is buggy on bigger maps

appveyor.yml

@@ -1,7 +1,7 @@
 image: Visual Studio 2017
-version: 19.03-build{build}
+version: 20.03-build{build}
 environment:
-  version: 19.03
+  version: 20.03
 install:
 - ps: >-
     mkdir $env:TEMP\openloco

src/openloco/version.cpp

@@ -1,7 +1,7 @@
 #include "openloco.h"
 
 #define NAME "OpenLoco"
-#define VERSION "19.03"
+#define VERSION "20.03"
 
 namespace openloco
 {