Split Block: Add a character option for clarity

This also allows the split block to be used more easily in a HOF

blocks.js

@@ -836,6 +836,7 @@ SyntaxElementMorph.prototype.labelPart = function (spec) {
                 null, // text
                 false, // numeric?
                 {
+                    'character' : ['character'],
                     'whitespace' : ['whitespace'],
                     'line' : ['line'],
                     'tab' : ['tab'],

threads.js

@@ -2148,6 +2148,9 @@ Process.prototype.reportTextSplit = function (string, delimiter) {
         break;
     case 'whitespace':
         return new List(str.trim().split(/[\t\r\n ]+/));
+    case 'character':
+        del = '';
+        break
     default:
         del = (delimiter || '').toString();
     }