does not convert to latest PAGE schema by default

[bertsky]

When converting some older version, e.g. http://schema.primaresearch.org/PAGE/gts/pagecontent/2010-03-19, I have to explicitly use -convert-to LATEST, or otherwise nothing will be changed.

In trying to understand why, I came up with this hypothesis:

• targetFormat is initialized null
• it does not get set unless -convert-to is used
• if using LATEST, then 2019 is selected
• and used
• otherwise, the default format comes from readPage
• which in turn just gets the default XmlPageReader
• creating a XmlModelAndValidatorProvider
• which uses the default PageXmlModelAndValidatorProvider
• whose getLatestSchemaVersion
• is supposed to be the last entry among the defaultSchemas, i.e. the 2019 version
• however, because schemaVersion is never assigned in XmlPageReader
• the parser is initialized
• for the 2019 version anyway
• nevertheless that does seem to set a Page.formatVersion from the file, not the parser
• because that is what is used for writing in the end