fpspreadsheet: Add reading/writing of boolean cell values for BIFF formats. 
Add test case for boolean cell values for all formats (incl. CSV). 
Extend spready demo to be able to write sfExcel2 and sfExcel5 formats.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3656 8e941d3f-bd1b-0410-a28a-d453659cc2b4
fpspreadsheet: Forgot to add celltypetests unit to repository...

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3657 8e941d3f-bd1b-0410-a28a-d453659cc2b4