Update sample to use a modified version of the default attribute inspector skin to showcase validation.

Sample now supports validation through a custom skin that uses the new field classes,
CalendarField dateFormat and DoubleField fractionalDigits.  FieldInspector now also supports a required
property.
Modified version of the default attribute inspector skin to showcase validation.

Custom skin that uses the new field classes, CalendarField dateFormat and
DoubleField fractionalDigits.
Merge branch '#11/update-attr-insp-sample-use-validator-skin' into develop