Added two new buttons and other enhancements

Added buttons for:

Change scanning direction (ascending / descending)

Saving current freq into the SCANNER.TXT file

(Please notice that, on the other hand -for safety issues- the DEL FQ button, deletes the frequency only from the temp memory on the actual scanning session, but does NOT erases the freq. inside the SCANNER.TXT)

Also there are other bug fixes and scanning speed enhancements.