Dir set to synch

Let the user select a set of dirs to synchronize, instead of the main and sec dirs.

For example, consider the following sets of dirs as main and sec:

* main
    * c:\movies
    * c:\itamar\music
    * c:\itamar\docs
* sec
    * d:\media\movies
    * d:\media\music
    * d:\docs_backup

Reported by: itamarc