Quick fix for POJO support - JavaBeanIntegerPropertyElement was being
used instead of JavaBeanDoublePropertyElement for Double variables
POJO support - FX was throwing a NPE when trying to access null Integer
values.

This is an internal FX bug
(http://javafx-jira.kenai.com/browse/RT-23980)
Checking if the field is "synthetic" when iterathing the list of
properties.

This way, generated methods are ignored in the traversal, like the
Groovy __$stMT, $staticClassInfo and others.