Added simulation parameters (DF y OF).

The services layer can read simulation parameters. These parameters are
passed to the SimulationManager, which use them to configure properly
the EnergyAgents module. The simulation parameters included in this
commit are:

 - DF: number of directory facilitators.
 - OF: the overbooking factor.
Bug fixed: definition of the Singleton scope in Guice.
Adapted injection modules to work with the experiment Exp04.
Added property for specifying the order of the sellers.