Update dataValidation to match spec
The spec suggests that showInputMessage and showErrorMessage should be optional and default to False. Updated DataValidation class to match
Ref. https://c-rex.net/projects/samples/ooxml/e1/Part4/OOXML_P4_DOCX_dataValidation_topic_ID0E1DW4.html
Closes 1732 and potentially 1770
--HG-- branch : 3.0
Edited by snippet