Added Openloops as a new external, added OpenLoops to the sherpa configu...

Added Openloops as a new external package. Downloads all existing processes and compiles them. openloops.cfg contains gFortran flag needed for long directory names. Total size of all *.so files 470MB
You want:

```
cat \EOF >>  openloops.cfg
[OpenLoops]
fortran_compiler = gfortran
gfortran_f90_flags = -ffixed-line-length-0 -ffree-line-length-0
EOF
```