fpspreadsheet: Fix ODS writer beginning to write rows/columns at first used row/column instead of 0. ODS error message test active now. Separate errortests and virtualmodetests from internaltests. All tests passed (Win32, Laz trunk, fpc 2.6.4).

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3449 8e941d3f-bd1b-0410-a28a-d453659cc2b4