fpspreadsheet: Registration of currency symbols. Add currency dialog to spready. Automatic detection of currencies in in worksheet.WriteCellAsNumber. Avoid redundant code in csv reader's currency detection.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3698 8e941d3f-bd1b-0410-a28a-d453659cc2b4