fpspreadsheet: Add properties for direct cell font access by TsWorksheetGrid.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3040 8e941d3f-bd1b-0410-a28a-d453659cc2b4
fpspreadsheet: Pass visibility of gridlines and sheet headers from TsWorksheetGrid to underlying Worksheet for saving.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3041 8e941d3f-bd1b-0410-a28a-d453659cc2b4