Using date picker for example prep description

Author: cafarm

src/main/resources/examples/+io/+github/+symphony_das/+sources/Preparation.m

@@ -7,7 +7,8 @@
 
             obj.addProperty('protocol', '', ...
                 'description', 'The preparation protocol implemented to obtain the specific sample');
-            obj.addProperty('date', '', ...
+            obj.addProperty('date', datestr(now), ...
+                'type', PropertyType('char', 'row', 'datestr'), ...
                 'description', 'The date the preparation protocol was performed to obtain the specific sample');
             obj.addProperty('region', '');
             obj.addProperty('sliceThickness', 0, ...