Datafilter String Support - 1 of 4

.. Strings and vectors of strings are useful for plotting bar charts
   or wherever category variables are needed, they are also useful
   when working with xdata names and metadata within ride files.

.. Full support for strings will be introduced over the next 4
   commits, including this one (1 of 4):

   1 - Basics - Create, Assign, Coerce, isString
   2 - Operators - Logical, Math etc
   3 - Functions - sort, uniq, aggregate etc
   4 - String Functions - cat, split, toupper/lower etc

.. Will wait until all 4 commits are completed and string support
   is feature complete before updating the wiki.

src/Gui/SearchFilterBox.cpp

@@ -89,7 +89,7 @@ SearchFilterBox::matches(Context *context, QString filter)
         DataFilter df(NULL, context, spec);
         foreach(RideItem *item, context->athlete->rideCache->rides()) {
             Result res = df.evaluate(item, NULL);
-            if (res.isNumber && res.number)
+            if (res.isNumber && res.number())
                 returning << item->fileName;
         }
     }