BUG #13984: Expose 'HeaderType' for XML writers.

Exposing HeaderType property of XML writers to enable selecting of 64-bit
headers, if requested.

Also fixing pqWriterDialog to use the newer pqProxyWidget to create the
auto-generated panel.

Updating pqProxyWidget to support legacy 'show="0"' Hint type to hide
properties.

Change-Id: Id613a1c8f6ecdf81d1640e33192324e6dc884f52
Update VTK to bring writer fixes.

Change-Id: Ib10d2fa0dff696aef63949f2ef11edc9ce97c535
Merge topic '13984_64bit_headers_for_xml_writers' into next

4c1ddd3 Update VTK to bring writer fixes.
40d1994 BUG #13984: Expose 'HeaderType' for XML writers.