The navigation pane is used in all dashboards but its markdown contents are duplicated in every one.

This should be moved out into its own file and then inserted into the appropriate place when dashboards is imported.

• dashboards/dashboards/navigation.md will hold the markdown for the navigation pane
• all dashboards will have MALCOLM_NAVIGATION_MARKDOWN_REPLACER in the place of this content
• dashboards/scripts/shared-object-creation.sh will do the replace of MALCOLM_NAVIGATION_MARKDOWN_REPLACER with the actual contents (escaped) of dashboards/dashboards/navigation.md
• the dashboard export API will put the replacer in on export