Add convenience XmlOptions setter methods with boolean arguments

I would suggest that XmlOptions was extended with convenience methods like
public XmlOptions setSavePrettyPrint(boolean flag)
for all the no-arg setters.

This would also allow us to do stuff like
XmlOptions customOptions = new XmlOptions(standardOptions).setSavePrettyPrint(false);
There is currently no elegant way of turning off options.

In addition, this would allow us to configure XmlOptions as part of our spring configuration. For example:

<bean name="saveXmlOptions" class="org.apache.xmlbeans.XmlOptions">
<property name="saveNamespacesFirst" value="true">
<property name="savePrettyPrint" value="true">
</bean>

This is not currently possible, since the spring cannot call no-arg setters, so we have to use a custom BeanFactory.