1. Modified six-panel summary code, added loop and `figcontents` dictionary
2. Changed six-panel summary graph legend to global, added subtitles to subplots
3. Added illustration on  
```
self.initdata = vars(self).copy()
```
and 
```
if init == True:
     for para in self.initdata:
         setattr(self, para, self.initdata[para])
```

----

modified panel summary code, added illustration

Add code for malthusian model