Minor tweaks to shadow warning infrastructure

1. Moved some methods out of boot.js because they are not needed until
after bootup
2. Added alternate message for editing an overridden shadow tiddler
3. Minor style tweaks

core/modules/utils/utils.js

@@ -33,6 +33,23 @@ exports.count = function(object) {
 	return s;
 };
 
+/*
+Check if an array is equal by value and by reference.
+*/
+exports.isArrayEqual = function(array1,array2) {
+	if(array1 === array2) {
+		return true;
+	}
+	array1 = array1 || [];
+	array2 = array2 || [];
+	if(array1.length !== array2.length) {
+		return false;
+	}
+	return array1.every(function(value,index) {
+		return value === array2[index];
+	});
+};
+
 /*
 Push entries onto an array, removing them first if they already exist in the array
 	array: array to modify (assumed to be free of duplicates)
@@ -481,6 +498,6 @@ exports.timer = function(base) {
 		m = m - base;
 	}
 	return m;
-}
+};
 
 })();