Setters and getters more intuitive

I think setters and getters could be more intuitive for manipulating data. 
```
   hole.fileheader['KJ'] 
   hole.header.XY["X"]
   hole.header.XY["Y"]
   etc..
```

And it should be ensured that it handels pointers and copys correctly.

```
hole = holes[0]
hole.fileheader['KJ']  = "system"
```

changes all holes