Added direct force plugin and fixes in stretching energy

Samo Penic

2019-03-09 2c4278db6ead5c27e30a3000097ed898c968534e

 src/plugins/stretching_energy.c

@@ -2,10 +2,8 @@
#include<math.h>

#include "general.h"
#include "vertex.h"
#include "cell.h"
#include "vesicle.h"
#include "frame.h"
#include "energy.h"

char plugin_name[] = "Stretching energy";
char plugin_description[]= "Plugin adds stretching energy to Monte Carlo steps";
char plugin_author[] = "SAMO PENIC";
@@ -58,9 +56,10 @@
         stretchenergy(vesicle, vtx->tristar[i]);
         data->dstretchenergy+=vtx->tristar[i]->energy;
         }
   }
   return data->dstretchenergy;
}
   return 0.0;
}