Improve handling of double square brackets within tags

Now a [[ has to be preceded by the beginning of the string or a
whitespace and a ]] has to be followed by whitespace or the end of the
string to act as quotes.

Thanks to @Skeeve for the regex

boot/boot.js

@@ -269,7 +269,7 @@ $tw.utils.stringifyList = function(value) {
 // Parse a string array from a bracketted list. For example "OneTiddler [[Another Tiddler]] LastOne"
 $tw.utils.parseStringArray = function(value) {
 	if(typeof value === "string") {
-		var memberRegExp = /(?:\[\[([^\]]+)\]\])|([^\s]+)/mg,
+		var memberRegExp = /(?:^|\s)(?:\[\[(.*?)\]\])(?=\s|$)|(\S+)/mg,
 			results = [],
 			match;
 		do {