Bug fixed: Creating the Directory Facilitator of the ASPEM.

ASPEM has to create their own DF agents. This feature wasn't fully
implemented. Now each ASPEM creates as many DF agents as the
configuration file says.

 - ASPEM creates and kill the DF agents during the execution of the
auction.
 - Added a new property to the configuration file that defines the
number of running DF agents per ASPEM.
Bug fixed: IdAuction out of sync.

The ASPEM was incrementing the Id of the Auction in the wrong moment, so
that later processes were using an incorrect auction's id.
Bug fixed: Send abort message where there are not consumers.

At the start stage, when there are not consumers, the Abort message is
sent to all the agents. Previously, it was being sent to the agents
there were passing to the next stage (it didn't make sense).