fpspreadsheet: Add tool for measuring writing and reading speeds for various file sizes and options. Based on a tool by rvk (http://forum.lazarus.freepascal.org/index.php/topic,25142.msg152919.html#msg152919).

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3354 8e941d3f-bd1b-0410-a28a-d453659cc2b4