Review configuration parameters page for 7.4

See NXP-17813: some of the properties listed on https://doc.nuxeo.com/x/QQA7 will be documented on the explorer instead after the release (when explorer holds the 7.4 distribution)

Some notes about needed changes:

• link to the explorer doc, explaining that some properties can be defined through runtime extension points now (TODO AT: provide the text)
• remove the properties that have been migrated to extension points:
  • studio.snapshot.disablePkgValidation
  • nuxeo.pageprovider.default-max-page-size
  • org.nuxeo.dnd.*
  • org.nuxeo.query.builder.ignored.chars
  • nuxeo.ui.displayEmailInUserSuggestion
  • nuxeo.jsf.enableDoubleClickShield
  • nuxeo.jsf.useAjaxTabs
  • nuxeo.path.segment.maxsize
  • org.nuxeo.ecm.platform.query.nxql.defaultNavigationResults
  • nuxeo.text.annotations
  • nuxeo.logs.viewer.max.lines.count

Also some properties are now obsolete:

• org.nuxeo.ecm.webapp.dashboard.mode: opensocial vs JSF dashboard conf (no opensocial dashboard anymore on 7.4)
• theme.useOldLocalConfiguration: obsolete since theme removal