Import/Export page user Interface

A interface to import/export a Wiki page in XML should be added.
It should be done using the /exportpage/ /importpage/ action.

A few options should be available on export and import:

For both:

x Include versions
x Include attachments

For import

x Update author (on import) -> use the current author or the author coming from the import
x Update date -> use the current date or the date coming from the import

This will to toFullXML and fromXML