fpspreadsheet: Some fixes in fpspreadsheetgrid and spready demo (tabcontrol instead of pagecontrol for spreadsheetgrid, hang of TsWorksheetGrid due to bug in new code related to merged cells, updates of inspector, better handling of the file-not-found situation, improved commandline interface for spready).

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3547 8e941d3f-bd1b-0410-a28a-d453659cc2b4