sPFFramework/src/main/java/it/polimi/spf/framework/SPF.java
synchronized static void initialize(Context context, int goIntent, boolean isAutonomous, ProximityMiddleware.Factory factory) {
        if (singleton == null) {
            singleton = new SPF(context, goIntent, isAutonomous, factory);
        }
    }
synchronized static void initialize(Context context, int goIntent, boolean isAutonomous, ProximityMiddleware.Factory factory) {
        if (singleton == null) {
            singleton = new SPF(context, goIntent, isAutonomous, factory);
        }
    }
Initializes SPF with a {@link Context} reference. Called by
{@link SPFContext#initialize(int, Context, ProximityMiddleware.Factory)}.

@param context - the context that will be used by SPF