Add minimum client version check code (#2), modify critical error handling,

bump version to 1.5.2

www/js/main.js

@@ -56,6 +56,7 @@ function onDeviceReady() {
     });
 }
 
+
 /**
  * Compare two version strings.
  * http://stackoverflow.com/a/16187766/2534036
@@ -79,6 +80,7 @@ function compareVersions(a, b) {
     return segmentsA.length - segmentsB.length;
 }
 
+
 function serverProblemsDialog(errmsg) {
     window.location = "servererror.html?errmsg=" + errmsg;
 }