V3.6 upgrade processing - reset theme

.. based upon current background plot color, so those with a
   preference for dark themes get the new dark theme and those
   with a preference for light get the new light theme.

.. making it mandatory will likely annoy some users but for the
   most part it will mean the UI will get updated to a more
   thoughtful color scheme.

src/Core/GcUpgrade.cpp

@@ -376,6 +376,16 @@ GcUpgrade::upgrade(const QDir &home)
         CloudServiceFactory::instance().upgrade(home.dirName());
     }
 
+    //----------------------------------------------------------------------
+    // 3.6 upgrade processing
+    //----------------------------------------------------------------------
+    if (last < VERSION36_BUILD) {
+
+        // reset themes on basis of plot background (first 2 themes are default dark and light themes
+        if (GCColor::luminance(GColor(CPLOTBACKGROUND)) < 127)  GCColor::applyTheme(0);
+        else GCColor::applyTheme(1);
+
+    }
 
     //----------------------------------------------------------------------
     // ... here any further Release Number dependent Upgrade Process is to be added ...

src/Core/GcUpgrade.h

@@ -100,6 +100,7 @@
 // 4004 - V3.6 DEVELOPMENT 2106 (JUN 2021)
 // 4005 - V3.6 DEVELOPMENT 2107 (JUL 2021)
 
+
 #define VERSION3_BUILD    3010 // released
 #define VERSION3_SP1      3030 // released
 #define VERSION3_SP2      3032 // released
@@ -109,14 +110,14 @@
 #define VERSION33_BUILD   3933 // development release
 #define VERSION34_BUILD   3955 // released
 #define VERSION35_BUILD   3990 // released
-#define VERSION36_BUILD   4005 // development build July 2021
+#define VERSION36_BUILD   4006 // testing upgrade processing
 
 // will keep changing during testing and before final release
 #define VERSION31_BUILD VERSION31_UPG
 
 // the next two will with each build/release
-#define VERSION_LATEST 4005
-#define VERSION_STRING "V3.6-DEV2107"
+#define VERSION_LATEST 4006
+#define VERSION_STRING "V3.6-DEVELOPMENT"
 
 // default config for this release cycle
 #define VERSION_CONFIG_PREFIX "http://www.goldencheetah.org/defaults/3.5"