The program should have a graceful exit 

Hi @ANGSD 

when the program doesn't get the proper arguments, it dies with a `segmentation fault`. It would be nice to have a graceful exit

```
$ /vol/cloud/geogenetics/opt/bin/metaDMG++ lca -h
#/vol/cloud/geogenetics/opt/bin/metaDMG++ lca -h
        -> Must supply arguments in the form -pattern value
Segmentation fault (core dumped)
```
